Question

Factorise the following:

(x + 3)(x – 3) – 40

Answer 1

The given expression is,

(x + 3)(x – 3) – 40

= x² – 9 – 40

= x² – 49

Here we use the identity

a² – b² = (a + b)(a – b)

Taking a = x and b = 7, we get

∴ (x + 3)(x – 3) – 40

= x² – 7²

= (x + 7)(x – 7)

Thus, the fully factorised form is (x + 7)(x – 7)