Question

x^4-3x^2=-2x^2

Answer 1

add 2x^2 to both sides to get
x^4 - x^2=0
Now factor out the x^2:
x^2(x^2-1) = 0.
We factor that out again because x^2 - 1 is a difference of two squares:
x^2 (x+1)(x-1) = 0
So we know that x = 0, x = 1, and x = -1 are solutions