SOLUTION: To solve this you want to write it: x^4 + 11x^2 - 80 = 0

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Question 634984: To solve this you want to write it:
x^4 + 11x^2 - 80 = 0
Answer by lwsshak3(11628) About Me  (Show Source):
You can put this solution on YOUR website!
solve for x
x^4 + 11x^2 - 80 = 0
**
let u=x^2
u^2=x^4
..
u^2+11u-80=0
(u+16)(u-5)=0
..
u=-16=x^2
x=±√-16
x=±4i (non-real solution)
..
u=5=x^2
x=±√5
check:
(x^4 + 11x^2 - 80 = 0
(√5)^4+11(√5)^2-80
25+55-80=0