Question

Which of the following is a polynomial with roots 5, 4i, and -4i?

F(x)=x^3-5x^2+20x-16
F(x)=x^3-5x^2+16x-80
F(x)=x^3-20x^2+5x-16
F(x)=x^3-16x^2+80x-5

Answer 1

you can just check the root x=5 by substitution. that will narrow your answer down to one choice. :)

Answer 2

e.g \[5^3-16*5^2+80*5-5\ne0\]