equations 5.3 notes - mastering-mathematics
Post on 24-Dec-2021
8 Views
Preview:
TRANSCRIPT
1
EQUATIONS
OUTLINE
• Linear Equations
• Literal Equations
• Quadratic Equations
• Cubic Equations
• Linear Inequalities
• Simultaneous Equations
1
2
2
LINEAR EQUATIONS
• solve complex linear equations involving algebraic fractions
LINEAR EQUATIONS
Linear equations have exactly one solution.
eg. Solve 2𝑥 1 3 𝑥 1
3
4
3
EQUATIONS WITH FRACTIONS
Solve:
𝑥 13
𝑥2
5
PRONUMERALS ON THE BOTTOM
When pronumerals are on the bottom, we treat the fractions exactly
the same.
2𝑥
32𝑥
11𝑥
5
6
4
BINOMIAL NUMERATORS OR DENOMINATORS
Solve:
𝑥 23
𝑥 54
BINOMIAL NUMERATORS OR DENOMINATORS
Solve
𝑥𝑥 1
3𝑥 1
1
7
8
5
LITERAL EQUATIONS
• change the subject of formulas
LITERAL EQUATIONS
A literal equation has more than one variable. We cannot solve a literal
equation unless we do simultaneous equations. We can change the
subject of the equation.
Make y the subject of 2𝑥 3𝑦 5.
9
10
6
LITERAL EQUATIONS
We can change the subject of a formula to make it easier to solve
questions.
Find the value of h if 𝑉 120 and 𝑟 6 by changing the subject of the formula 𝑉 𝜋𝑟 ℎ.
LITERAL EQUATIONS
Make r the subject of 𝐴 𝜋𝑟 .
11
12
7
LITERAL EQUATIONS
Make 𝑟 the subject of 𝑆𝑎
1 𝑟.
QUADRATIC EQUATIONS
• solve equations of the form 𝑎𝑥 𝑏𝑥 𝑐 0 by factorisation and by 'completing the square’
• use the quadratic formula to solve quadratic equations
• identify whether a given quadratic equation has real solutions, and whether or not they are equal
• solve a variety of quadratic equations and check the answers through substitution
• substitute a pronumeral to simplify higher‐order equations in order to solve them
• solve quadratic equations resulting from substitution into formulas or through solving problems and check their solutions
13
14
8
QUADRATIC EQUATIONS
Recall that quadratic equations may have one, two or no solutions.
𝑥 0
𝑥 1
𝑥 9
FACTORISING AND SOLVING
For quadratic trinomials, we can factorise and use the null factor law to
solve the equation.
𝑥 3𝑥 2 0Null Factor Law:
If 𝐴 𝐵 0 then
either 𝐴 0 or 𝐵 0.
15
16
9
FACTORISING AND SOLVING
Solve the following equations:
𝑥 2𝑥 63 0
3𝑥 5𝑥 12 0
CHECKING SOLUTIONS
Like all equations, we can check if our solutions are correct by
substituting back into the equation.
3𝑥 5𝑥 12 0
𝑥 3,43
17
18
10
COMPLETING THE SQUARE
What happens if we cannot factorise?
Solve 𝑥 6𝑥 5 0
EXAMPLE
Solve 𝑥 4𝑥 6 0 by completing the square.
19
20
11
THE QUADRATIC FORMULA
Solve the equation 𝑎𝑥 𝑏𝑥 𝑐 0.
THE QUADRATIC FORMULA
Given any quadratic equation in the form 𝑎𝑥 𝑏𝑥 𝑐 0 we can
find the solutions of the equation by using the formula:
𝑥𝑏 𝑏 4𝑎𝑐
2𝑎
The solutions to a quadratic equation are called the roots or zeroes. They are the x‐intercepts of the graph of the equation.
21
22
12
THE QUADRATIC FORMULA
Use the quadratic formula to find the roots of the equation 𝑥 6𝑥 5 0.
THE QUADRATIC FORMULA
Find the roots of the equation to 3𝑥 𝑥 18 0 to 3 significant
figures.
23
24
13
EQUATIONS REDUCIBLE TO QUADRATICS
Solve 𝑥 13𝑥 36 0
EQUATIONS REDUCIBLE TO QUADRATICS
By making an appropriate substitution, solve the equation:
2 4 5 2 2 0
25
26
14
THE DISCRIMINANT
There is a quick way to determine whether a quadratic equation has
zero, one or two solutions. All we need to do is calculate the expression
under the square root in the quadratic formula.
𝑥𝑏 𝑏 4𝑎𝑐
2𝑎This is called the discriminant and has the symbol ∆.
THE DISCRIMINANT
Let’s look at some examples:
a 𝑥 5𝑥 3 0
b) 𝑥 6𝑥 9 0
c) 2𝑥 4𝑥 7 0
𝑥5 25 4 3
25 13
2
𝑥6 36 4 9
26 0
23
𝑥4 16 4 2 7
2 24 40
4
27
28
15
THE DISCRIMINANT
A quadratic equation has:
• Two real roots if ∆ 0
• One real root if ∆ 0
• No real roots if ∆ 0
EXAMPLE
Use the discriminant to find the number of solutions to the following
quadratic equations:
a 2𝑥 𝑥 9 0 ∆ 1 4 2 9 71 none
b) 𝑥 5𝑥 11 0 ∆ 5 4 1 11 69 two
c) 4𝑥 12𝑥 9 0 ∆ 12 4 4 9 0 one
d) 𝑥 6𝑥 12 0 ∆ 6 4 1 12 84 two
29
30
16
THE DISCRIMINANT
There is one other piece of information we can get from the
discriminant. We can tell whether a quadratic can be factorised or not.
eg. Find the discriminant of the following:
2𝑥 𝑥 6 ∆ 1 4 2 6 49
3𝑥 𝑥 5 ∆ 1 4 3 5 61
2𝑥 𝑥 3 ∆ 1 4 2 3 25
Two of these can be factorised. Which ones?
If the discriminant is a perfect square, the answer will be _________.
EQUATIONS FROM FORMULAE
The cosine rule is a formula that finds unknown sides or angles of a non
right angled triangle:
𝑐 𝑎 𝑏 2𝑎𝑏𝑐𝑜𝑠𝐶
31
32
17
WORD PROBLEMS
A skydiver jumps from a plane. The height above the ground after tseconds is given by ℎ 1900 5𝑡 .
a) What height was the plane when the skydiver jumped?
b) Approximately how many seconds will it take for the skydiver to
reach the ground?
WORD PROBLEMS
A skydiver jumps from a plane. The height above the ground after tseconds is given by ℎ 1900 5𝑡 .
c) How many seconds does it take for the skydiver to fall 1000m?
33
34
18
WORD PROBLEMS
The product of two consecutive, positive integers is 342. What are the
numbers?
CUBIC EQUATIONS
• solve simple cubic equations of the form 𝑎𝑥 𝑘, leaving answers in exact form and as decimal approximations
35
36
19
CUBE ROOT
Unlike square root, when we take the cube root there is only one
solution.
Why?
27 3
CUBIC EQUATIONS
The highest power of a cubic equation is 3.
A cubic equation can have one, two or three solutions.
Solve the following cubic equations:
The opposite operation of 3 is ∛.
37
38
20
LINEAR INEQUALITIES
• solve linear inequalities, including through reversing the direction of the inequality sign and graph the solutions
LINEAR INEQUALTIES
Recall the two rules for solving inequalities:
• if we turn the inequality around (that is, swap sides) the inequality sign flips
• if we multiply or divide by a negative the sign flips
39
40
21
EXAMPLES
Solve, and graph the solution on a number line:
2𝑥 1 𝑥 2 2𝑥 1 3𝑥 1
HARDER INEQUALITIES
Inequalities can have three parts to them. For example:
2 𝑥 1 5
This means that 𝑥 1 lies between 2 and 5.
We can solve this inequality by applying opposite operations to all
three sides.
41
42
22
HARDER INEQUALITIES
Solve 1 1 2𝑥 5.
SIMULTANEOUS EQUATIONS
• use analytical methods to solve simultaneous equations, where one
equation is non‐linear
• use graphical methods to solve simultaneous equations, where one
equation is non‐linear
43
44
23
SIMULTANEOUS EQUATIONS
Recall that there are three methods of solving simultaneous equations:
• Elimination
• Substitution
• Graphical
When one of the equations is non‐linear, it is not practical to use the
elimination method.
SUBSTITUTION METHOD
Solve the following simultaneous equations:
𝑦 𝑥 3𝑥 1
𝑦 2𝑥 5
45
46
24
SUBTITUTION METHOD
Solve the following simultaneous equations.
𝑦2𝑥
𝑦 𝑥 1
GRAPHICAL METHOD
Solve the simultaneous equations by
graphing and finding the points of
intersection.
𝑦2𝑥
𝑦 𝑥 1
x -2 -1 0 1 2
y
x -2 -1 0 1 2
y
47
48
top related