SOLUTION: What cubic polynomial has roots -4 and 2i

SOLUTION: What cubic polynomial has roots -4 and 2i

Algebra.Com

Question 1156705: What cubic polynomial has roots -4 and 2i
Answer by Boreal(15235) (Show Source): You can put this solution on YOUR website!
the third root is -2i, since complex numbers come in conjugates
(x+4)=0
x+2i=0
x-2i=0
multiply the second and third together and get x^2-4i^2 or x^2+4
multiply that by (x+4)
x^3+4x^2+4x+16

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