What are the solutions of the equation x^4+3x^2+2=0? use u substitution to solve.

Let u=x^2
so the original equation becomes u^2+3u+2=0
factor: (u+1)(u+2)=0
u=-1 or u=-2
which means x^=-1, or x^2=-2
Since a number squared is never a negative number, there are no real solutions.