if you combine like terms yes but would that work if you left them apart?
x^4+x^2=1
1+1=1????
and if you combined like terms i could see it working but i don't think they should be combined may be wrong tho =p
There is a very simple technique to solve this.
You just replace x^2 =a to get a simpler equation.
then x^4+x^2=1 -> a^2+a=1
solve a
solve x
???
profit