## anonymous 4 years ago How would you solve x^4=2x^2 - 1?

1. anonymous

still not understanding..

2. campbell_st

rewrite it as $x^4 - 2x^2 + 1 = 0$ let $u = x^2$ solve u^2 -2u+ 1 = 0 which is (u - 1)^2 = 0 then u = 1 is a solution but since u = x^2 then x^2 = 1 or $x = \pm$

3. campbell_st

oops $x = \pm 1$

4. anonymous

where'd u come from is what I'm curious of?

5. anonymous

IT MAKES SENSE NOW!!! THANKYOU