find the value(s) of x for which f(x)=g(x).

Question

f(x)=x^4-2x^2,g(x)=2x^2

Answer 1

set them equal, and solve for x

x^4-2x^2=2x^2
x^4-4x^2=0
(x^2-2x)(x^2+2x)=0
x^2(x-2)(x+2)=0
and now you have four solutions (two zeroes).