1.

Factorize each of the following algebraic expressions:x2 – 4x – 21

Answer»

As given,

x2 – 4x – 21

By considering, p+q = -4 and pq = -21

So we can replace -4x by 3x – 7x

-21 by 3 × -7

x2 + 4x – 21

= x2 + 3x – 7x – 21

= x (x + 3) – 7 (x + 3)

= (x – 7) (x + 3)



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