Question

finding zeros

Answer 1

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

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

Answer 2

HInt: if -2i is a zero, then x = -2i and x = 2i

Answer 3

thats a givin.... dont i have to simplify it to something that multiplies to 100 but adds up to 21? which would be 25*-4..... but idk where to go from there

Answer 4

You can also take that approach as well. Since (25)(-4) = -100 and 25 - 4 = 21, then you can substitute:

x^4 - (25 - 4)x^2 - 100
x^4 - 25x^2 + 4x^2 - 100

Then finish factoring by grouping

Answer 5

x^2 (x^2 -25) + 4 (x^2 -25)
(x^2 +4) (x^2 -25)
is that right?

Answer 6

(x^2 - 25) can be factored further right?

Answer 7

yeah (x-5)(x+5) so those are the other zeros then