Q3 of 157 Page 22

Using the identity (x + a)(x + b) = x2 + (a + b)x + ab, find out the following products:

(5x + 3)(5x + 4)

Given (5x + 3)(5x + 4)


Using (x + a)(x + b) = x2 + (a + b)x + ab


(5x + 3)(5x + 4)= (5x)2 + (3 + 4)5x + 3×4


⇒ (5x + 3)(5x + 4)= 25x2 + 35x + 12


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