Mathway is a great tool for more advanced Math functions.
It will even show you the steps taken to solve a problem, if you create an free account.
It still supports basic math problems, but it also has tools for:
Geometry, Pre-Algebra, Algebra, Linear Algebra, Trigonometry, Precalculus, Calculus, Statistics, and Probability.
While the interface takes some time to get use to, it rewards you by allowing you to do such operations as: