# How do you solve #x^4 – 8x^2 – 9 = 0#?

##### 1 Answer

Feb 11, 2016

x can be 3, -3, i, or -i.

#### Explanation:

If you can't find the factoring by looking at this, simplify the equation.

let

Now we have

See it now?

We can factor into

Now substitute back in

Since

Now we have

x can be 3, -3 for the first two parts

Taking the positive and negative root means

Thus