SOLUTION: I'm looking for the answer to the question x^4-81x^2=0 I know it's GCF but what is the answer?

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Question 289931: I'm looking for the answer to the question
x^4-81x^2=0
I know it's GCF but what is the answer?
Found 2 solutions by Fombitz, Earlsdon:
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
x%5E4-81x%5E2=0
x%5E2%28x%5E2-81%29=0
Use the zero product rule,
x%5E2=0
highlight%28x=0%29
.
.
.
x%5E2-81=0
x%5E2=81
highlight%28x=-9%29, highlight%28x=9%29

Answer by Earlsdon(6294) About Me  (Show Source):
You can put this solution on YOUR website!
Solve for x: There will be four solutions.
x%5E4-81x%5E2+=+0 Factor x%5E2
x%5E2%28x%5E2-81%29+=+0 Apply the zero product rule:
x%5E2+=+0 or x%5E2-81+=+0 so
x+=+0
x+=+0
x+=+9
x+=+-9