1.

Find the following products :(y - 7) (y + 3)

Answer»

Using the identity : (x + a) (x + b) = x2 + (a + b) x + ab, we have

 (y - 7) (y + 3) = {y + (-7)} (y + 3) 

 = y2 + {(-7) + 3} + (-7) × 3 

 = y2 - 4y - 21. 



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