Question

Factorize the following algebraic expression : $x^2-4x-21$

Answer 1

Given : $x^2-4x-21$
On splitting the middle term , we get
$x^2+3x-7x-21$
$=x(x+3)-7(x+3)$
$=(x-7)(x+3)$

Hence, $x^2-4x-21=(x-7)(x+3)$