Question

How do you factor `y=5x^4+10x^2-15` ?

Answer 1

First factor you can take out is `5`

Explanation:

`=5(x^4+2x^2-3)`

Now if you see `x^2` as a whole (let's call `x^2=z` just for now) you have a quadratic expression you can factor further:
`=5(z^2+2z-3)=5(z+3)(z-1)`

Translated back, this becomes:
`=5(x^2+3)(x^2-1)`

And you can factor the last term even further:
`=5(x^2+3)(x-1)(x+1)`