Finding the roots is equivalent to finding the x-intercepts of its graph and this is done by setting y = 0:

If the product of two integers is equal to 0, then either one or both are 0. Let's see what x values would make each factor equal to 0:

So one root is x = 2.

As for the other one, it requires the quadratic formula:

Simplify the radical and you'll get your desired answer.