Question

How do you factor by grouping `x^3-12-3x^2+4x`?

Answer 1

Have a look:
Collect between the 1st and 3rd term and between 2nd and 4th:

Answer 2

`x^3 -12-3x^2+4x`
can be re-grouped as
`(x^3-3x^2) +(4x-12)`
which can then be factored as
`(x^2)(x-3) + (4)(x-3)`
then combining the common factor from each term
`(x^2+4)(x-3)`