SOLUTION: x^4-9x^2+20=0

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Question 549327: x^4-9x^2+20=0
Answer by KMST(5328) About Me  (Show Source):
You can put this solution on YOUR website!
If you changed variables to y=x%5E2
it would simplify into
y%5E2-9y%2B20=0 which you would factor to get %28y-4%29%28y-5%29=0, so
x%5E4-9x%5E2%2B20=0 factors into %28x%5E2-4%29%28x%5E2-5%29=0
It further factors into
%28x%2B2%29%28x-2%29%28x%2Bsqrt%285%29%29%28x-sqrt%285%29%29=0
The 4 real solutions to that equation are:
x=-2, x=2, x=-sqrt%285%29, and x=sqrt%285%29