hard math formulas or concepts
DESCRIPTION
Math Concepts on Algebra and StatisticsTRANSCRIPT
n = 3 (1+2+3)/3 = 6/3 = 2n = 7 (2+3+4+5+6+7+8)/7 = 35/7 = 5
n = 2 (1+2)/2 = 1.5 n=4 (3+4+5+6)/4 =4.5
n = 2 (1.2)/2! = 1 n=5 (3.4.5.6.7)/5! =4.5
ODD Divisible
EVEN NOT Divisible
Multiple of N ± Multiple of N = Multiple of N
Multiple of N ± Non-Multiple of N = Non-Multiple of N
Non Multiple of N + Non Multiple of N = Multiple or Non-multiple of N
(X^3-Y^3) = (X-Y)(X^2+XY+Y^2)
xn - yn = ( x - y ) (xn-1 + xn-2y + ... + xyn-2 + yn-1 )
Because (x2 – y2 ) = (x-y)(x+y)X4-y4 =(x2-y2)(x2+y2) = (x+y)(x-y)(x2+y2)
(a + b)3 = a3 + 3a2b + 3ab2 + b3 (a - b)3 = a3 - 3a2b + 3 ab2 - b3
a3 - b3 = (a - b)3 + 3 a b (a - b)
a3 - b3 = (a - b) (a2 + a b + b2)
a3 + b3 = (a + b)3 - 3 a b (a + b)
a3 + b3 = (a + b) (a2 - a b + b2)
a b = ((a + b) / 2)2 - ((a - b) / 2)2
2.25
2.45
2.85
Inequalities
Inequality Flips No-Flip
Multiply by –ve number Flips
Taking Reciprocal Flip (When both numbers have same sign)
No-flip( when they have different sign)
Squaring
Addition, Substraction, Square root etc does not change inequality
No-Flip
Eg -2 > -3 => -1/2 < -1/3
3 > 2 => 1/3 < 1/2
If the signs are same then
Reciprocal will flip the inequality
If the signs are different then
Reciprocal will not flip the inequality
Squaring will flip the ineq if both numbers are negative (both side multiplied by –ve number)
Operation Mean Median Mode Range StandardDev
ai ± k(increased decreased by k)
Mean ± k Median ± k
Mode ± k Does Not Change
Does Not Change
ai × k Mean × k Median × k
Mode × k Range × k SD × k
ai / k Mean / k Median / k
Mode / k Range / k SD / k
Mean = Average (Sum/# of elements)Median = middle number (consec numbers median = mean, n=odd=> median=int)Mode = most frequentRange = max - minSD = Sqrt(Variance) Variance = Ʃ (mean – xi)2 / # of terms n
Statistics