Question

how do I factor x^4-3x^2-4

Answer 1

first, can I troll a little?

Answer 2

let y= x^2 then think of it as:

y^2-3y-4 then you have:

(y+1)(y-4)

so:

(x^2 +1 ) (x^2 -4)

now keep factoring:

(x^2 +1)(x-2)(x+2)

For high school math you'd stop here but, you can factor it more if you are using imagery numbers...

(x-i)(x+i)(x-2)(x+2)

where i = sqrt(-1)

Hence the expression would have 4 roots when set equal to zero as expected.