Q1 of 227 Page 103

Solve the following quadratic equations by factorization method.

(2x + 3)2 – 81 = 0

(2x + 3)2 – 81 = 0


= (2x)2 + 2(2x)(3) + 32 – 81 = 0


= 4x2 + 12x + 9 –81 = 0


= 4x2 + 12x – 72 = 0


Divide by 4 both sides


⇒


= x2 + 3x – 18 = 0


= x2 + 6x – 3x – 18 = 0


= x (x + 6) – 3 (x + 6) = 0


= (x + 6) (x – 3) = 0


x + 6 = 0 or x – 3 = 0


x = –6 or x = 3


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