Question

Factorise 12a²b+ 15ab².

Answer 1

We have

12a²b = 2 × 2 × 3 × a × a × b.

15ab² = 3 × 5 × a × b × b.

The two terms have 3, a, and b as common factors.

Therefore,

12a²b + 15ab² 

= (3 × a × b × 2 × 2 × a ) + (3 × a × b × 5 × b)

= 3 × a × b × [(2 × 2 × a) + (5 × b)]         ...(combining the terms)

= 3ab × (4a + 5b)

= 3ab(4a + 5b)                                          ...(required factor form)