Question

How do you factor `x^4 -3x^2 -4= 0`?

Answer 1

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

Explanation:

Call `x^2 = X`, the trinomial transforms itself to -->
`y = X^2 - 3X - 4.`
Since a - b + c = 0, use shortcut.
The 2 factors are: (X + 1) and`(X + c/a = X - 4).`
`y = (X + 1)(X - 4) = (x^2 + 1)(x^2 - 4) =`
`= (x^2 + 1)(x - 2)(x + 2)`