So we want to find a way to put your equation into that form. The first step is to move the constant term to the other side of the equation:
Now, we want to add something to the left hand side to make it a perfect square. Look at that form again. If we can find what a is, then we need to simply add . So look at the linear term, -3x in your case. We want to find a value for a, so set
So we need to add
to the left hand side. But what we do to one side of the equation, we need to do to the other. Thus
The left hand side is now in perfect square form. Simplifying the left and right hand sides gives:
Can you solve it from here?