Question

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

2 - 4i is a zero of f(x).= x4 - 4x3 + 21x2 - 4x + 20

Answer 1

as the coefficient are real numbers then another root is 2+4i

Answer 2

(x-2+4i)(x-2-4i)=x^2-4x+20
so divide f(X) to x^2-4x+20
you have degree 2
then you can do it your own
try it
hint :f has 4 unreal root

Answer 3

f(x)= (x2-4x+20)(x2+1)
so the roots are
x= 0+i , 0-i , 2-4i , 2+4i

Answer 4

is anybody there ?