Question

I know the AC method but that only works with 3 variables (I think that’s the word)

This has four
Someone please help
Thank you

Answer 1

You can do this by grouping:

`3x^3+9x^2-2x-6=3x^2(x+3)-2(x+3)=(3x^2-2)(x+3)`

You could continue to factor
`3x^2-2=(\sqrt3\,x)^2-(\sqrt2)^2` as a difference of squares so that

`3x^3+9x^2-2x-6=(\sqrt3\,x+\sqrt 2)(\sqrt3\,x-\sqrt2)(x+3)`

`3x^3+9x^2-2x-6=3\left(x+√(\frac23)\right)\left(x-√(\frac23)\right)(x+3)`