Question

Factorise by substituting terms:

12(a + b)² – 5(a + b) – 3

Answer 1

12(a + b)² – 5(a + b) – 3

Let a + b = y

= 12y² – 5y – 3

= 12y² – 9y + 4y – 3

= 3y(4y – 3) + 1(4y – 3)

= (4y – 3) (3y + 1)

= [4 (a + b) – 3] [3 (a + b) + 1]

= (4a + 4b – 3) (3a + 3b + 1)