Question

Using the given zero, find all other zeros of f(x).

-2i is a zero of f(x) = x^4 - 21x^2 - 100

Answer 1

Here are the choices (:

2i, 10, -10

2i, 5, -5

2i, 10i, -10i

2i, 5i, -5i

Answer 2

if all coefficent are real numbers
then
if a+ib is root a-ib is also root of equation

Answer 3

so another root is +2i
divide f(x) to (x+2i)(x-2i)

Answer 4

another solution is to use "a=x^2"
so f=a^2-21a-100

Answer 5

So, would the answer be 2i, 5, -5???

Answer 6

yes

Answer 7

Thank you so much!! :D