Useless
This app is just about as close as you can possibly get to completely useless. It's a good thing he isn't making you pay for it because even after using it for only 20 seconds I was incredibly amazed at how unintuitive the UI was. Say you are entering numbers into the quadratic equation, if you realize after entering all three that the you accidentally entered the first number incorrectly, you have to enter each again, there is no way to only change the single incorrect number. I'm a developer and I can't imagine this app took any longer than 10 minutes to write.
