2x^4-2x^2-81=x^2(x^2-2)

Question

2x^4-2x^2-81=x^2(x^2-2)

Answer 1

2х^4-2х^2-81=х^2(х^2-2)
2х^4-2х^2-81-х^2(х^2-2)=0
2х^4-2х^2-81-х^4+2х^2=0
х^4=81
х=3