SOLUTION: n=4; i and 2i are zeros; f(-1)=20

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Question 975247: n=4; i and 2i are zeros; f(-1)=20
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
I'm assuming you need real coefficients so you use complex conjugate roots.
y=a%28x-i%29%28x%2Bi%29%28x-2i%29%28x%2B2i%29
y=a%28x%5E2%2B1%29%28x%5E2%2B4%29
y=a%28x%5E4%2B4x%5E2%2Bx%5E2%2B4%29
y=a%28x%5E4%2B5x%5E2%2B4%29
When x=-1, y=20
20=a%28%28-1%29%5E4%2B5%28-1%29%5E2%2B4%29
20=a%281%2B5%2B4%29
20=a%2810%29
a=2
So,
highlight%28y=2x%5E4%2B10x%5E2%2B8%29
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