OK, here's the trick:
|We'll take the square root:|
Squares and square roots undo each other... Right?
Now, remember our equation rules -- whatever we do to one side, we have to do to the other. So, we'll take the square root of both sides:
Uh oh... We only got one answer. Hmm... We got two answers when we factored.
Here's what you officially do to fix this problem: