Question

Factorise the following expression:

−16z + 20z³

Answer 1

16z = −1 × 2 × 2 × 2 × 2 × z

20z³ = 2 × 2 × 5 × z × z × z

The common factors are 2, 2, and z.

∴ −16z + 20z³ = −1 (2 × 2 × 2 × 2 × z) + (2 × 2 × 5 × z × z × z)

= (2 × 2 × z) [−1 (2 × 2) + (5 × z × z)]

= 4z (− 4 + 5z²)