Q25 of 137 Page 100

Factories:

9a2 – b2 + 4b – 4

Given,


9a2 – b2 + 4b – 4


= 9a2 – (b2 – 4b + 4)


By using the formula a2 – b2 = (a + b)(a – b)


We get,


9a2 – b2 + 4b – 4 = 9a2 – (b2 – 4b + 4)


= (3a)2 – (b – 2)2


= {3a + (b – 2)}{3a – (b – 2)}


= (3a + b - 2)(3a – b + 2)


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