When I was a junior in high school and entered into Algebra 2 the big concept everyone was worried about was the quadratic equation. They were right. This app helps students not only solve those equations but also how to do it and even more. There are plenty of choices to explain what each part it is, how to handle square roots etc. It’s free and if you’re a teacher or student who works with quadratic equations this is a pretty good app (it was free when I downloaded it, now it costs $0.99). You can get it here.