Question

Factorise the following:

1 – 18a – 63a²

Answer 1

Given expression: 1 – 18a – 63a²

We have to find two numbers whose sum is –18 and whose product is –63. 

These numbers are –21 and 3.

Now, using middle term factorisation method,

1 – 18a – 63a²

= 1 – 21a + 3a – 63a²

= (1 – 21a + 3a) (1 – 21a)

= (1 – 21a)(1 + 3a)

The factorisation result is (1 – 21a) (1 + 3a).