How do I solve $x^4-3x^2+2=0$? How do I solve $x^4-3x^2+2=0$ ?
I would appreciate some kind of hint here.  I have no clue how to start this problem. 

Consider the product $(y-2)(y-1)$ for which the expansion is $y^2 - 3 y +2$. Now let $y = x^2$ to obtain $x^4 - 3 x^2 + 2 = (x^2 -2)(x^2 -1) = 0$. This leads to $x^2 = 2$ or $x^2 =1$. These two equations yields $x \in \{ - 1, 1, - \sqrt{2}, \sqrt{2} \}$. 
