Question

x^4 + 6x^2 - 40 = 0
x^2 = t

Apparently the answers are x1=2, x2=-2

I'm getting -10 and 4. What am I doing wrong...?

Answer 1

i bet u got t as 4 and -10
but x is \(\sqrt t\)
so taking only real values. x=+ or -2

Answer 2

Aaaaaahhhh.... yeah, facepalm. Thanks. :)

Answer 3

I've been staring at that for way too long.

Answer 4

other 2 imaginary roots, + or - \(\sqrt 10\)i