SOLUTION: x4 + 3x2 = -1 solve fro x

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Question 726920: x4 + 3x2 = -1 solve fro x
Answer by tanjo3(60) About Me  (Show Source):
You can put this solution on YOUR website!
x%5E4+%2B+3x%5E2+=+-1
x%5E4+%2B+3x%5E2+%2B+1+=+0
Let u be x^2.
u%5E2+%2B+3u+%2B+1+=+0
Using the quadratic formula:
u+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+
u+=+%28-3+%2B-+sqrt%28+3%5E2-4%2A1%2A1+%29%29%2F%282%2A1%29+
u+=+%28-3+%2B-+sqrt%28+5+%29%29%2F2+
u+=+%28-3+%2B+sqrt%28+5+%29%29%2F2+, u+=+%28-3+-+sqrt%28+5+%29%29%2F2+
Substitute back u=x^2.
x%5E2+=+%28-3+%2B+sqrt%28+5+%29%29%2F2+, x%5E2+=+%28-3+-+sqrt%28+5+%29%29%2F2+
x+=+%2B+sqrt%28%28-3+%2B+sqrt%28+5+%29%29%2F2%29+, x+=+-+sqrt%28%28-3+%2B+sqrt%28+5+%29%29%2F2%29+, x+=+%2B+sqrt%28%28-3+-+sqrt%28+5+%29%29%2F2+%29, x+=+-+sqrt%28%28-3+-+sqrt%28+5+%29%29%2F2+%29