Square root of both sides If you have the equation:
$x^2=2$
You get:
$x=\pm \sqrt{2}$
But what do you do actually do? What do you multiply both sides with to get this answer? You take the square root of both sides, but the square root of what? If you understand what i mean? 

$$x^2=2 \Rightarrow \begin{cases}y=x^2\\y=2 \end{cases}$$

