Question

factorise (a+b)^2+10(a+b)+21 class 9

Answer 1

${(a + b)}^{2} + 10(a + b) + 21$

Let (a+b) be x. then,

${x}^{2} + 10x + 21$

$= {x}^{2} + 3x + 7x + 21$

$= x(x + 3) + 7(x + 3)$

$= (x + 3)(x + 7)$

$= (a + b + 3)(a + b + 7)$

HOPE IT HELPS