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    Home > Quantitative aptitude questions and answers with explanation > Numbers > Important Concepts and Formulas - Algebra

    Important Concepts and

    Formulas - Numbers

    Important Concepts and

    Formulas - Algebra

    Important Concepts and

    Formulas - Sequence and

    Series

    Important Concepts and

    Formulas - Logarithms

    Important Concepts and

    Formulas - Trigonometry

    Important Concepts and

    Formulas - Complex

    Numbers

    Solved Examples - Set 1

    Solved Examples - Set 2Solved Examples - Set 3

    Important Concepts and Formulas - Algebra

     

    I. Basic Algebraic Formulas 

    1. (Distributive Law)

    2.

    3.

    4.

    5.

    6.

    7.

    8.

    9.

    10.

    11.

    12.

    01.2kLike Share

    Java RDBMS Quantitative Aptitude Online Tests Aptitude Q&A Speed Mathematics Scientif ic Cal culator Miscellaneous

    a    (   b    +     c   ) =     a b   

    +    a c   

    (   a    +     b   = + 2    a b   

    +    

    )  

    2   

    a   

    2   

    b   

    2   

    (   a    −     b   = − 2    a b   

    +    

    )  

    2   

    a   

    2   

    b   

    2   

    (   a    +     b   + (  

    a    −     b   = 2 ( + )    

    )  

    2   

    )  

    2   

    a   

    2   

    b   

    2   

    (   a    +     b   = + 3   

    b   + 3   

    a   + = + 3      a b   

    (   a    +     b   ) +    

    )  

    3   

    a   

    3   

    a   

    2   

    b   

    2   

    b   

    3   

    a   

    3   

    b   

    3   

    (   a    −     b   = − 3   

    b   + 3   

    a   − = − 3      a b   

    (   a    −     b   ) −    

    )  

    3   

    a   

    3   

    a   

    2   

    b   

    2   

    b   

    3   

    a   

    3   

    b   

    3   

    − = (  a    −     b   

    ) (  a    +     b    )  

    a   

    2   

    b   

    2   

    + = (  a    +     b   

    ) ( −     a b    + )  

    a   

    3   

    b   

    3   

    a   

    2   

    b   

    2   

    − = (  a    −     b   

    ) ( +     a b    + )  

    a   

    3   

    b   

    3   

    a   

    2   

    b   

    2   

    − = (  a    −     b   

    ) ( +    b   

    + + . . . + )    

    a   

        

    b   

        

    a   

        − 1  

    a   

        − 2   

    a   

        − 3   

    b   

    2   

    b   

        − 1  

    (   a    +     b    +     c   = + + + 2 (    a b   

    +    b c   

    +    c a   

    )  

    )  

    2   

    a   

    2   

    b   

    2   

    c   

    2   

    (   a    +     b   ) (  

    a    +     c   ) = + (    

    b    +     c    )   a    +    b c   

    a   

    2   

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    1.

    2.

    3.

    4.

    5.

    6.

    7.

    8.

    9.

    10.

    11.

    12.

    13.

    1.

    2.

    3.

    4.

    5.

    6.

    7.

    8.

    =     a    .  a    .  a    . . . ( n t i m e s )    

    a   

        

    . . . . =        a   

         

    a   

        

    a   

        

    a   

          +         + . . . +        

        

    . =    a   

         

    a   

        

    a   

          +         

    =    

    a   

         

    a   

        

    a   

          −         

    = =    ( )  a   

         

        

    a   

        

    ( )  a   

        

         

    =    (  a b   

    )  

        

    a   

        

    b   

        

    =        

    a   

    b   

        

    a   

        

    b   

        

    =    a   

    −         

    1  

    a   

        

    =    a   

        

    1  

    a   

    −         

    = 1 w h e r e a   

    ∈ R , a ≠ 0      a   

    0   

    =    a   

         /       

    a   

        

    − −    

    √     

       

    i f = w h e r e a   

    ≠ 0 a n d a   

    ≠ ± 1 , t h e n       =         a   

         

    a   

        

    i f = w h e r e     

    ≠ 0 , t h e n a   

    = ±    b   a   

        

    b   

        

    (     

    +    a    = + 2   

    a    

    +    )  

    2   

       

    2   

    a   

    2   

    (       −     a   = − 2    a    

    +    )  

    2   

       

    2   

    a   

    2   

    (       +     a   ) (  

        +     b   ) = + (    

    a    +     b    )       +    a b   

       

    2   

    − = (      −     a   

    ) (      +     a    )     

    2   

    a   

    2   

    ( + 1 ) i s c o m p l e t e l y d i v i s i b l e b y ( x + 1 ) w h e n n i s o d d         

        

    ( + ) i s c o m p l e t e l y d i v i s i b l e b y ( x + a ) w h e n n i s o d d         

        

    a   

        

    ( − ) i s c o m p l e t e l y d i v i s i b l e b y (        −     a   

    ) f o r e v e r y n a t u r a l n u m b e r n         

        

    a   

        

    ( − ) i s c o m p l e t e l y d i v i s i b l e b y (        +     a   

    ) w h e n n i s e v e n         

        

    a   

        

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    Binomial Theorem 

    If a and b are any real numbers and n is a positive integer,

    Binomial Coefficient also occurs in many other mathematical areas than algebra, especially in combinatorics wher

    represents the number of combinations of n distinct things taking r at a time and is denoted by nCr or C(n,r).

    The properties of binomial coefficients have led to extending its meaning beyond the basic case where n and r are nonn

    integers with r ≤ n; such expressions are also called binomial coefficients.

    Binomial Expansions 

    ... and so on

    Binomial Series 

    One of Newton's achievement was to extend the Binomial Theorem to the case where

    n can be any real number.

    If n is any real number and -1 < x < 1, then

    II. Surds and Important Properties 

    i. Surds

    Let be a rational number and be a positive integer such that is irrational.

    Then is called a surd of order n.

    (   a    +     b    )  

        

    = +     b    + + + ⋯ + + ⋯a   

        

    a   

        − 1  

         (       − 1 )  

    2 ! 

    a   

        − 2   

    b   

    2   

         (       − 1 ) (    

        − 2 )  

    3 ! 

    a   

        − 3   

    b   

    3   

         (       − 1 ) (    

        − 2 ) ⋯ (    

         −        + 1 )  

        ! 

    a   

         −        

    b   

       

    =         +         b    +         +        + ⋯ +    

       + ⋯ +    

       

        

    0   

    a   

        

        

    1  

    a   

        − 1  

        

    2   

    a   

        − 2   

    b   

    2   

        

    3   

    a   

        − 3   

    b   

    3   

        

       

    a   

         −        

    b   

       

        

        

    b   

        

    =        ∑    

       = 0   

        

        

       

    a   

         −        

    b   

       

    w h e r e    

    i s k n o w n a s B i n o m i a l C o e f f i c i e n t a n d i s d e f i n e d b y      

        

       

        = = w h e r e r = 1 , 2 , . . . , n a n d     = 1  

        

       

         ! 

    (      ! ) (  

         −        ) ! 

         (       − 1 ) (    

        − 2 ) ⋯ (    

         −        + 1 )  

        ! 

        

    0   

    (   a    +     b   = 1  

    )  

    0   

    (   a    +     b    =     a    +     b   )  

    1  

    (   a    +     b   = + 2    a b   

    +    )  

    2   

    a   

    2   

    b   

    2   

    (   a    +     b   = + 3   

    b   + 3   

    a    +    )  

    3   

    a   

    3   

    a   

    2   

    b   

    2   

    b   

    3   

    (   a    +     b   = + 4   

    b   + 6 + 4      

    a    +    )  

    4   

    a   

    4   

    a   

    3   

    a   

    2   

    b   

    2   

    b   

    3   

    b   

    4   

    ( 1 +        )  

        

    = 1 +         + + + ⋯          

         (       

    − 1 )  

    2 ! 

       

    2   

         (       

    − 1 ) (    

        

    − 2 )  

    3 ! 

       

    3   

    =        +    

       +    

       +    

       + ⋯      

        

    0   

       

    0   

        

    1  

       

    1  

        

    2   

       

    2   

        

    3   

       

    3   

    =        ∑    

       = 0   

    ∞     

        

       

       

       

    w h e r e    

    = w h e r e r ≥ 1 a n d    

    = 1  

        

       

         (       − 1 ) (    

        − 2 ) ⋯ (    

         −        + 1 )  

        ! 

        

    0   

    a a   

    √     

        

    a   

    √     

        

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    Examples :

     is a surd of order 2

     is a surd of order 3

     is a surd of order 2

    Please note that numbers like , etc are not surds because they are not

    irrational numbers

    Every surd is an irrational number. But every irrational number is not a surd. (eg

    : , etc are not surds though they are irrational numbers.)

    ii. Quadratic Surds

    A surd of order 2 is called a quadratic surd

    Examples :

    iii. Rules of Surds

    1.

    2.

    3.

    4.

    5. if

    1. The conjugate surd of

    2. if and are quadratic surds and if ,then and

    i.e., rational part on the lef t side = rational part on the right side.

    and irrational part on the left side = irrational part on the right side.

    3. if and are quadratic surds and if ,

    then and

    III. Quadratic Equations and How to Solve Quadratic Equations 

    A. Quadratic Equations

    A quadratic equation is a second degree univariate polynomial equation.

    A quadratic equation can be written as (general form or standard form of quadratic

    equation)

    where x is a variable, a, b and c are constants and

    Example :

    (Please note that if a=0, equation becomes a linear equation)

    The solutions of a quadratic equation are called its roots.

    B. How to Solve Quadratic Equations

    There are many methods to solve Quadratic equations. Quadratic equations can be

    solved by factoring, completing the square, graphing, Newton's method, and using the

    quadratic formula. We can go through some of the popular methods for solving

    quadratic equations here.

    3   √     

    7   √     

    3   

    4 3   √     

    9   √ 2 7   

    − −    

    √     

    3   

    π    

    , , ( 3 + ) , e t c .  2   

    √     

    3   √ 5   

    √     

    × =         

    − −    

    √     

        

    √     

        

    − −    −    

    √     

    =    

         

    − −    

    √     

        

    √     

         

        

    − −    −    

    √     

    =    a    .  a    .  a   ⋯ n t i m e s    

    − −    − − − − − − − −        

    √     

    − −    − − − − − − − − − − −        

    √     

    − −    − − − − − − − − − − − − − − −        

    √   

    a   

    1 −    

    1  

    2   

        

    =    a   a   

    . a   

    . a    ⋯ ∞     

    − −    − − − −        

    √     

    − −    − − − − − − −        

    √     

    − −    − − − − − − − − − − −        

    √   

    =         , t h e n     

    (       − 1 ) =        a   a   

    +    a   

    +    a    ⋯ ∞     

    − −    − − − −        

    √     

    − −    − − − − − − − − −        

    √     

    − −    − − − − − − − − − − − − − −        

    √   

    + = ± ( − )    a   

    √     

    b   

    √     

    a   

    √     

    b   

    √     

    b   

    √     

       

    √     

    a    + =     c   +    

    b   

    √     

       

    √     

    a   =    

    c b   

    =       

    b   

    √     

       

    √     

    a   + =    

    b   

    √     

       

    √     

    a   = 0   

    b    =        

    a    +    b    

    +     c   = 0   

       

    2   

    a   ≠ 0   

    + 5        + 6 = 0      

       

    2   

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    1. How to Solve Quadratic Equations By Factoring

    Step 1: Write the quadratic equation in standard form.

    i.e. , bring all terms on the left side of the equal sign and 0 on the right side of 

    the equal sign.

    Step 2: Factor the left side of the equation

    Step 3: Equate each factor to 0 and solve the equations

    Factoring is one of the fastest ways for solving quadratic equations. The concept

    will be clear from the following examples.

    Example1 : Solve the Quadratic Equation

    Step 1 : Write the quadratic equation in standard form.

    Step 2 : Factor the left side of the equation.

    We know that . We will use the same

    concept for factoring.

    Assume

    We need to find out a and b such that a + b = 3 and ab = -10

    a = +5 and b = -2 satisfies the above condition.

    Hence

    Step 3 :Equate each factor to 0 and solve the equations

    (x + 5)(x - 2) = 0

    => (x + 5) = 0 or (x - 2) = 0

    => x = -5 or 2

    Hence, the solutions of the quadratic equation are x = -5

    and x = 2.

    (In other words, x = -5 and x = 2 are the roots of the quadratic equation

    Example2 : Solve the Quadratic Equation

    This equation is already in the standard form. Hence let's go to step 2

    Step 2 : Factor the left side of the equation.

    Here we need to find out a and b such that a + b = -7 and ab = +10

    a = -5 and b = -2 satisfies the above condition.

    Hence

    Hence,

    Step 3 :Equate each factor to 0 and solve the equations

    (x - 5)(x - 2) = 0

    => (x - 5) = 0 or (x - 2) = 0

    => x = 5 or 2

    Hence, the solutions of the quadratic equation are x = 5 and x

    + 4      

    − 1 1 =           

    − 1     

    2   

    + 4        − 1 1 =            − 1  

       

    2   

    ⇒ + 4      

    − 1 1 −           

    + 1 = 0      

       

    2   

    ⇒ + 3      

    − 1 0 = 0      

       

    2   

    + (  a    +     b    )       +    

    a b    = (      +     a   

    ) (      +     b    )  

       

    2   

    + 3      

    − 1 0 = + (    a    +     b    )       +    

    a b   

       

    2   

       

    2   

    + 3      

    − 1 0 = (       

    + 5 ) (       

    − 2 )  

       

    2   

    + 3      

    − 1 0 = 0      

       

    2   

    ⇒ (     

    + 5 ) (       

    − 2 ) = 0      

    + 4      

    − 1 1 =           

    − 1  

       

    2   

    + 4      

    − 1 1 =           

    − 1  

       

    2   

    − 7      

    + 1 0 = 0      

       

    2   

    − 7      

    + 1 0 = (       

    − 5 ) (       

    − 2 )     

    2   

    + 3      

    − 1 0 = 0         

    2   

    ⇒ (     

    − 5 ) (       

    − 2 ) = 0      

    − 7      

    + 1 0 = 0         

    2   

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    = 2.

    (In other words, x = 5 and x = 2 are the roots of the quadratic equation

    )

    Example3 : Solve the Quadratic Equation

    This equation is already in the standard form. Hence let's go to step 2

    Step 2 : Factor the left side of the equation.

    Here we need to follow a slightly different approach for factoring because here

    the coefficient of x2 ≠ 1 (whereas In example 1 and example 2, the coefficient of 

    x2 was 1)

    Hence, to factor , we need to do the followings

    1. Product of the second degree term and the constant. i.e.,

    2. We got product as 24x2 and have middle term as -14x. From this , it is clear

    that we can take -12x and -2x such that their sum is -14x and product is 24x 2

    Hence, =

    Hence,

    Step 3 :Equate each factor to 0 and solve the equations

    (x - 5)(x - 2) = 0

    => (x - 4) = 0 or (3x - 2) = 0

    => x = or .

    Hence, the solutions of the quadratic equation are x = and

    x =

    (In other words, x = and x = are the roots of the quadratic equation

    Example4 : Solve the Quadratic Equation

    This equation is already in the standard form. Hence let's go to step 2

    Step 2 : Factor the left side of the equation.

    coefficient of x2 ≠ 1

    Hence, to factor , we need to do the followings

    1. Product of the second degree term and the constant. i.e.,

    2. We got product as 72x2 and have middle term as -17x. From this , it is clear

    that we can take -8x and -9x such that their sum is -17x and product is 72x 2

    Hence,

    Hence,

    Step 3 :Equate each factor to 0 and solve the equations

    (3x - 4)(2x - 3) = 0

    => (3x - 4) = 0 or (2x - 3) = 0

    => x = or .

    Hence, the solutions of the quadratic equation are x =

    and x = .

    − 7      

    + 1 0 = 0         

    2   

    3 − 1 4          + 8 = 0         

    2   

    3 − 1 4         

    + 8      

    2   

    3 × 8 = 2 4         

    2   

       

    2   

    3 − 1 4         

    + 8 = 0         

    2   

    3 − 1 2         

    − 2      

    + 8 = 3          (      

    − 4 ) − 2 (       

    − 4 ) = (       

    − 4 ) ( 3         

    − 2 )     

    2   

    3 − 1 4         

    + 8 = 0         

    2   

    ⇒ (     

    − 4 ) ( 3         

    − 2 ) = 0      

    4   

    2   

    3   

    3 − 1 4         

    + 8 = 0         

    2   

    4   

    2   

    3   

    4   

    2   

    3   

    3 − 1 4         

    + 8 = 0         

    2   

    6 − 1 7         

    + 1 2 = 0         

    2   

    6 − 1 7         

    + 1 2      

    2   

    6 × 1 2 = 7 2      

       

    2   

       

    2   

    6 − 1 7         

    + 1 2 = 6 − 8         

    − 9      

    + 1 2 = 2         

    ( 3      

    − 4 ) − 3 ( 3         

    − 4 ) = ( 3         

    − 4 ) ( 2         

    − 3 )  

       

    2   

       

    2   

    6 − 1 7         

    + 1 2 = 0      

       

    2   

    ⇒ ( 3      

    − 4 ) ( 2         

    − 3 ) = 0      

    4   

    3   

    3   

    2   

    6 − 1 7         

    + 1 2 = 0      

       

    2   

    4   

    3   

    3   

    2   

    4 3   

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    (In other words, x = and x = are the roots of the quadratic equation

    (Special Factorization Examples)

    Example5 : Solve the Quadratic Equation

    This equation is already in the standard form. Hence let's go to step 2

    Step 2 : Factor the left side of the equation.

    Here, is in the form where a = x and b = 3

    We know that We will use the same concept for

    factoring this.

    Hence,

    Step 3 :Equate each factor to 0 and solve the equations

    (x - 3)(x + 3) = 0

    => x = 3 or -3

    Hence, the solutions of the quadratic equation are x = 3 and x = -3

    (In other words, x = 3 and x = -3 are the roots of the quadratic equation

    Example6 : Solve the Quadratic Equation

    This equation is already in the standard form. Hence let's go to step 2

    Step 2 : Factor the left side of the equation.

    Hence,

    Step 3 : Equate each factor to 0 and solve the equations

    (5x - 4)(5x + 4) = 0

    =>5x = 4 or -4

    .

    Hence, the solutions of the quadratic equation are x = and x =

    (In other words, x = and x = are the roots of the quadratic equation

    Example7 : Solve the Quadratic Equation

    This equation is already in the standard form. Hence let's go to step 2

    Step 2 : Factor the left side of the equation.

    Here, is in the form where a = x and b = 3

    We know that We will use the same concept for

    factoring this.

    2   

    4   

    3   

    3   

    2   

    6 − 1 7         

    + 1 2 = 0         

    2   

    − 9 = 0         

    2   

    − 9      

    2   

    −    a   

    2   

    b   

    2   

    − = (  a    −     b   

    ) (  a    +     b    )  a   

    2   

    b   

    2   

    − 9 = − = (       

    − 3 ) (       

    + 3 )     

    2   

       

    2   

    3   

    2   

    − 9 = 0         

    2   

    ⇒ (     

    − 3 ) (       

    + 3 ) = 0      

    − 9 = 0         

    2   

    − 9 = 0         

    2   

    2 5 − 1 6 = 0         

    2   

    2 5 − 1 6 = ( 5         

    − = ( 5         

    − 4 ) ( 5         

    + 4 )     

    2   

    )  

    2   

    4   

    2   

    2 5 − 1 6 = 0         

    2   

    ⇒ ( 5      

    − 4 ) ( 5         

    + 4 ) = 0      

       = o r

    4   

    5   

    − 4   

    5   

    2 5 − 1 6 = 0         

    2   

    4   

    5   

    − 4   

    5   

    4   

    5   

    − 4   

    5   

    2 5 − 1 6 = 0         

    2   

    + 6      

    + 9 = 0         

    2   

    + 6      

    + 9      

    2   

    + 2    a b   +    a   

    2   

    b   

    2   

    + 2    a b    + = (  a    +     b   a   

    2   

    b   

    2   

    )  

    2   

    + 6      

    + 9 = + 2 ×         

    × 3 + = (       

    + 3      

    2   

       

    2   

    3   

    2   

    )  

    2   

    + 6      

    + 9 = 0      

    2   

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    Hence,

    Step 3 :

    => x + 3 = 0

    => x = -3

    Hence, the solution of the quadratic equation is x = -3

    (In other words, x = -3 is the root of the quadratic equation

    Example8 : Solve the Quadratic Equation

    This equation is already in the standard form. Hence let's go to step 2

    Step 2 : Factor the left side of the equation.

    Here, is in the form where a = x and b = 3

    We know that We will use the same concept for

    factoring this.

    Hence,

    Step 3 :

    => x - 3 = 0

    => x = 3

    Hence, the solution of the quadratic equation is x = 3

    (In other words, x = 3 is the root of the quadratic equation

    2. How to Solve Quadratic Equations By Quadratic Formula

    Quadratic Formula

    Consider a quadratic equation where

    Its solutions can be given by

    Example1 : Solve the Quadratic Equation

    Hence, the solutions of the quadratic equation are x = 2

    and x = -5

    (In other words, x = 2 and x = -5 are the roots of the quadratic equation

    + 6      

    + 9 = 0         

    2   

    ⇒ (     

    + 3 = 0      )  

    2   

    (      + 3 = 0      

    )  

    2   

    + 6      

    + 9 = 0         

    2   

    + 6      

    + 9 = 0         

    2   

    − 6      

    + 9 = 0         

    2   

    − 6      

    + 9      

    2   

    − 2    a b   +    a   

    2   

    b   

    2   

    − 2    a b    + = (  a    −     b   a   

    2   

    b   

    2   

    )  

    2   

    − 6      

    + 9 = − 2 ×         

    × 3 + = (       

    − 3      

    2   

       

    2   

    3   

    2   

    )  

    2   

    + 6      

    + 9 = 0         

    2   

    ⇒ (     

    − 3 = 0      )  

    2   

    (      − 3 = 0      

    )  

    2   

    − 6        + 9 = 0         

    2   

    − 6      

    + 9 = 0         

    2   

    a    +    b    

    +     c   = 0   

       

    2   

    a   ≠ 0   

        =    

    −     b   ± − 4    a c   

    b   

    2   

    − −    − − − − −        

    √     

    2   a   

    + 4      

    − 1 1 =           

    − 1     

    2   

    + 4      

    − 1 1 =           

    − 1     

    2   

    ⇒ + 4      

    − 1 1 −           

    + 1 = 0         

    2   

    ⇒ + 3      

    − 1 0 = 0         

    2   

       = = =    

    −     b   ± − 4    a c   

    b   

    2   

    − −    − − − − −        

    √     

    2    a   

    − 3 ± − 4 × 1 × ( − 1 0 )    3   

    2   

    − −    − − − − − − − − − − − − −        

    √   

    2 × 1  

    − 3 ± 9 + 4 0      

    − −    − − −    

    √     

    2   

    =    

    − 3 ± 7      

    2   

    = o r

    4   

    2   

    − 1 0   

    2   

    = 2 o r − 5      

    + 4        − 1 1 =            − 1     

    2   

    + 4      

    − 1 1 =           

    − 1     

    2   

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    Example2 : Solve the Quadratic Equation

    Hence, the solutions of the quadratic equation are x = 5 and x

    = 2.

    (In other words, x = 5 and x = 2 are the roots of the quadratic equation

    Example3 : Solve the Quadratic Equation

    Hence, the solutions of the quadratic equation are x = and

    x =

    (In other words, x = and x = are the roots of the quadratic equation

    Example4 : Solve the Quadratic Equation

    Hence, the solutions of the quadratic equation are x =

    and x = .

    (In other words, x = and x = are the roots of the quadratic equation

    Example5 : Solve the Quadratic Equation

    Hence, the solutions of the quadratic equation are x =(-3 + i)

    + 4      

    − 1 1 =           

    − 1     

    − 7      

    + 1 0 = 0         

    2   

       = = =    

    −     b   ± − 4    a c   

    b   

    2   

    − −    − − − − −        

    √     

    2   a   

    7 ± ( − 7 − 4 × 1 × 1 0      

    )  

    2   

    − −    − − − − − − − − − − − − −        

    √   

    2 × 1  

    7 ± 4 9 − 4 0      

    − −    − − − −        

    √     

    2   

    = =    

    7 ± 9   √     

    2   

    7 ± 3   

    2   

    = o r

    1 0   

    2   

    4   

    2   

    = 5 o r 2      

    − 7      

    + 1 0 = 0         

    2   

    − 7      

    + 1 0 = 0 )       

    2   

    3 − 1 4         

    + 8 = 0         

    2   

       = = =    

    −     b   ± − 4    a c   

    b   

    2   

    − −    − − − − −        

    √     

    2    a   

    1 4 ± ( − 1 4 − 4 × 3 × 8      )  

    2   

    − −    − − − − − − − − − − − − −        

    √   

    2 × 3   

    1 4 ± 1 9 6 − 9 6      

    − −    − − − − −        

    √     

    6   

    = =    

    1 4 ± 1 0 0      

    − −    −    

    √     

    6   

    1 4 ± 1 0      

    6   

    = o r

    2 4   

    6   

    4   

    6   

    = 4 o r

    2   

    3   

    3 − 1 4         

    + 8 = 0         

    2   

    4   

    2   

    3   

    4   

    2   

    3   

    3 − 1 4         

    + 8 = 0      

       

    2   

    6 − 1 7         

    + 1 2 = 0      

       

    2   

       = = =    

    −     b   ± − 4    a c   

    b   

    2   

    − −    − − − − −        

    √     

    2    a   

    1 7 ± ( − 1 7 − 4 × 6 × 1 2      )  

    2   

    − −    − − − − − − − − − − − − − −        

    √   

    2 × 6   

    1 7 ± 2 8 9 − 2 8 8      

    − −    − − − − − −        

    √     

    1 2   

    = =    

    1 7 ± 1    

    √     

    1 2   

    1 7 ± 1    

    1 2   

    = o r

    1 8   

    1 2   

    1 6   

    1 2   

    = o r

    3   

    2   

    4   

    3   

    6 − 1 7         

    + 1 2 = 0         

    2   

    4   

    3   

    3   

    2   

    4   

    3   

    3   

    2   

    6 − 1 7         

    + 1 2 = 0         

    2   

    + 6        + 1 0 = 0         

    2   

       = = =    

    −     b   ± − 4    a c   

    b   

    2   

    − −    − − − − −        

    √     

    2    a   

    − 6 ± ( 6 − 4 × 1 × 1 0      )  

    2   

    − −    − − − − − − − − − − − −        

    √   

    2 × 1  

    − 6 ± 3 6 − 4 0      

    − −    − − − −        

    √     

    2   

    = =    

    − 6 ± − 4      

    − −    −    

    √     

    2   

    − 6 ± 2        

    2   

    = − 3 ±          

    = ( − 3 +          

    ) o r ( − 3 −           )  

    + 6      

    + 1 0 = 0         

    2   

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    and x = (-3 - i)

    (In other words, x =(-3 + i) and x = (-3 - i) are the roots of the quadratic

    equation

    Example5 : Solve the Quadratic Equation

    Hence, the solutions of the quadratic equation is

    (In other words, is the roots of the quadratic equation

    Example6 : Solve the Quadratic Equation

    Hence, the solutions of the quadratic equation are x = 3 and x = -3

    (In other words, x = 3 and x = -3 are the roots of the quadratic equation

    C. How to find out the number of solutions(roots) of a quadratic

    equation quickly?

    To find out the number of solutions (roots) of a quadratic equation  quickly, we need to find out the discriminant, D. The

    discriminant, D =

    If the discriminant is positive, there will be two real solutions for the quadratic

    equation.

    If the discriminant is 0, there will be one real solution (it repeats itself) for the

    quadratic equation.

    If the discriminant is negative, there will be two complex solutions for the

    quadratic equation.

    Example1 :

    Find out the number of roots for

    Discriminant, D =

    D > 0. Hence will have two real roots.

    Let's verify if this is correct by solving the quadratic equation.

    Yes, two real roots we got.

    Example2 :

    Find out the number of roots for

    Discriminant, D =

    D = 0. Hence will have one real root (it repeats itself)

    Let's verify if this is correct by solving the quadratic equation.

    Yes, real root (it repeats itself).

    + 6      

    + 1 0 = 0         

    2   

    + 6        + 9 = 0         

    2   

       = = =    

    −    b    ± − 4   

    a c   

    b   

    2   

    − −    − − − − −        

    √     

    2    a   

    − 6 ±    

    ( − 6 − 4 × 1 × 9      )  

    2   

    − −    − − − − − − − − − − − −        

    √   

    2 × 1  

    − 6 ±    

    ( 3 6 − 3 6      

    − −    − − − − −        

    √     

    2 × 1  

    = =    

    − 6 ± 0      √     

    2   

    − 6   

    2   

    = − 3   

    + 6      

    + 9 = 0         

    2   

       = − 3   

       = − 3 + 6      

       + 9 = 0      

       

    2   

    − 9 = 0         

    2   

       = = =    

    −     b   ± − 4    a c   

    b   

    2   

    − −    − − − − −        

    √     

    2   a   

    0 ± ( 0 − 4 × 1 × ( − 9 )    )  

    2   

    − −    − − − − − − − − − − − − − −        

    √   

    2 × 1  

    ± 3 6   

    − −    

    √     

    2   

    = ±    

    6   

    2   

    = 3 o r − 3      

    − 9 = 0      

       

    2   

    − 9 = 0      

       

    2   

    a    +    b    

    +     c   = 0   

       

    2   

    – 4    a c   b   

    2   

    − 7      

    + 1 2 = 0         

    2   

    – 4    a c    = ( − ) − ( 4 × 1 × 1 2 ) = 4 9 − 4 8 = 1 .  b   

    2   

    7   

    2   

    − 7      

    + 1 2 = 0         

    2   

    − 7      

    + 1 2 = 0 ⇒ (       

    − 3 ) (       

    − 4 ) = 0 ⇒             

    = 3 o r 4 .     

    2   

    − 4      

    + 4 = 0         

    2   

    – 4    a c    = ( − ) − ( 4 × 1 × 4 ) = 1 6 − 1 6 = 0 .  b   

    2   

    4   

    2   

    − 4      

    + 4 = 0         

    2   

    − 4      

    + 4 = 0 ⇒ (       

    − 2 = 0 ⇒             

    = 2      

    2   

    )  

    2   

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    Example3 :

    Find out the number of roots for

    Discriminant, D =

    D < 0. Hence will have two complex roots

    Let's verify if this is correct by solving the quadratic equation.

    Yes, we got two complex roots, +i and -i

    D. Sum and Products of the roots of a quadratic equation

    Let and are the roots of a quadratic equation

    Sum of the roots of the quadratic equation,

    Product of the roots of the quadratic equation,

    Example 1: Find the sum and product of the roots of the quadratic equation

    sum of the roots

    product of the roots

    Example 2: Find the sum and product of the roots of the quadratic equation

    sum of the roots

    product of the roots

    Comments(6) Newest

    + 1 = 0         

    2   

    – 4    a c    = ( ) − ( 4 × 1 × 1 ) = 0 − 4 = − 4      b   

    2   

    0   

    2   

    + 1 = 0         

    2   

    + 1 = 0         

    2   

       = = = = = = ±

      

    −     b   ± − 4    a c   

    b   

    2   

    − −    − − − − −        

    √     

    2    a   

    0 ± − 4 × 1 × 1    0   

    2   

    − −    − − − − − − − − − −        

    √     

    2 × 1  

    0 − 4   

    − −    − − −    

    √     

    2   

    − 4   

    − −    −    

    √     

    2   

    ± 2  

    2   

       

    1  

       

    2   

    a    +    b    

    +     c   = 0 w h e r e

    a   ≠ 0   

       

    2   

    + =       

    1  

       

    2   

    −     b   

    a   

    × =       

    1  

       

    2   

    c   

    a   

    − 7      

    + 1 0 = 0         

    2   

    = = = 7      

    −     b   

    a   

    7   

    1  

    = = = 1 0      

    c   

    a   

    1 0   

    1  

    2 + 3      

    + 1 = 0         

    2   

    = =    

    −     b   

    a   

    − 3   

    2   

    = =    

    c   

    a   

    1  

    2   

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    SRK  30 Sep 2014 12:12 PM

    PLEASE HELP ME IN FINDING HCF AND LCM OF POLYNOMIALS

    Reshma  12 Jun 2014 11:11 AM

    very helpful site for students...:)

    catty  25 May 2014 5:09 PM

    so helpful guys! Thanks :)

    Parthiban  03 Mar 2014 6:06 PM

    This is help to me pls can you send me all the formulas

    vitthal  13 Feb 2014 1:26 PM

    give me problems

    Usama  28 Sep 2013 12:18 PM

    Can u mail me the formulae?

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