The one star reviews are harsh, unyielding, and expect the app to be something it’s not. This app is a clean, spare, dictionary of math formulas and concepts. All the info in a clear, easy to find place.
It assumes you’ve already learned the material, and need help remembering it. If you are not learning or haven’t already learned the concepts, this will not teach you.
It is not a magic wand, it’s not a teacher, and it’s not going to make the math itself easier. It’s simply a library of information that’s easily accessible. Khan academy and other online tools are not this. They are online math lessons, this is not.
For the people complaining about the price, it’s $3, far less than the cost of any book. The people who built it did an excellent job, and you’re able to test the app out for free. You don’t pay the money unless you decide the app works for you. If the app is not what you need, that doesn’t make it a 1 star app. The rating of apps is not about you.