If you are a student and you hate math class this will save your life no joke. My teacher helped develop it and it's about the best thing you can possibly imagine.
what does it do? pretty much any algebra question you need it to do, but I haven't fully explored its capabilities. So far I can tell you that it will graph for you and find every variation of line form for you, also it can factor and do other things. honestly just type what you want it to do or a type of math and put in the equation and BOOM its awesome. try it out and read the instructions cause i'm not very good at this so don't listen to my instructions haha.
link to the site: http://www.wolframalpha.com/