find all the zeros of the equation.

Question

-3x^4+27x^2+1200=0

I'm really confused, can someone help explain?

Answer 1

let z = x^2

-3 z^2 + 27 z + 1200 = 0
divide by -3

z^2 - 9 z - 400 = 0

(z-25)(z+16) = 0
z = 25 ---> x = 5 or -5
z = -16 --> x = 4 i or -4i