SOLUTION: solve equation: x^4+9x^2=-20

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Question 929593: solve equation: x^4+9x^2=-20
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
x%5E4%2B9x%5E2=-20
x%5E4%2B9x%5E2%2B20=0
Substitute u=y%5E2
u%5E2%2B9u%2B20=0
%28u%2B4%29%28u%2B5%29=0
Two "u" solutions:
u%2B4=0
u=-4
y%5E2=-4
y=2i and y=-2i
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u%2B5=0
u=-5
y%5E2=-5
y=sqrt%285%29i and y=-sqrt%285%29i