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? 

As $2=\left(\sqrt 2\right)^2$, we can transform $x^2=2$ into $x^2-\left(\sqrt 2\right)^2=0$, or $\left(x+\sqrt 2\right)\left(x-\sqrt 2\right)=0$. Now we use that a product is zero iff at least one of its factors is zero.

Alternatively, if you want to procede by applying something to both sides of the equation, this something is "taking the square root". This way $x^2=2$ implies that $\sqrt{x^2}=\sqrt 2$. Now you need to know that $\sqrt{x^2}=|x|$ for all real numbers $x$.
