Question

factorize : (a-3b)^2 - 4 (a-3b) - 21​

Answer 1

Answer:

(a - 3b - 7)(a - 3b + 3)

Step-by-step explanation:

   Let a - 3b = x

⇒ (a - 3b)^2 - 4(a - 3b) -21

⇒ x^2 - 4x - 21

⇒ x^2 - (7 - 3)x - 21

⇒ x^2 - 7x + 3x - 21

⇒ x(x - 7) + 3(x - 7)

⇒ (x - 7)(x + 3)

      Substitute x = a - 3b

⇒ (a - 3b - 7)(a - 3b + 3)

Answer 2

Answer:

It is already factorised

Step-by-step explanation:

$=(a-3b)^2-4(a-3b)-21\\\\\\=a^2-6ab+9b^2-4a+12b-21$