I'm not really sure how to isolate the absolute value expression.
I won't give the details, but another way would be to simply square the expression. . The downside is that you may have extra solutions, and instead of one inequality you have two: .
However, despite the downsides I like the logic inherent in this method slightly better, even if it makes the problem more difficult to solve. And, of course, when you are done you get earboth's answer.