SOLUTION: I have to solve this equation by making appropriate substitutions: x^4- 9x^2 = -20

SOLUTION: I have to solve this equation by making appropriate substitutions: x^4- 9x^2 = -20

Algebra.Com

Question 848794: I have to solve this equation by making appropriate substitutions:
x^4- 9x^2 = -20
Answer by fcabanski(1391) (Show Source): You can put this solution on YOUR website!

Substitute

(u-4)(u-5) = 0

u = 4 or 5

so x = + or - 2

so x = + or -

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