SOLUTION: find the root of the equation x^4-3x^2-54=0

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Question 378944: find the root of the equation x^4-3x^2-54=0
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
Use a substitution.
Let u=x%5E2, then u%5E2=x%5E4
u%5E2-3u-54=0
%28u-9%29%28u%2B6%29=0
Two solutions:
u-9=0
u=9
x%5E2=9
highlight%28x=0+%2B-+3%29
.
.
.
u%2B6=0
u=-6
x%5E2=-6
highlight%28x=0+%2B-+sqrt%286%29i%29