Question

How do you factor completely `7y^3 - 21y^2 - 2y + 6`?

Answer 1

`= color(green)((7y^2-2)(y-3)`

Explanation:

`color(blue)(7y^3-21y^2)color(green)(-2y+6`

Factorising by grouping :

`(7y^2)` is common to both the terms in the first group, and `-2` is common to both the terms in the second group:

We can factor this expression by making groups of two terms:
`7y^2(y-3) -2(y-3)`

`y-3` is common to both the terms now:

`= color(green)((7y^2-2)(y-3)`