One tool that can be used is Ellipse equation examples.
Any problem you need done it will do, it is very simple and easy to use, and I have not yet encountered anything wrong with it. Great for helping to understand formulas and checking my work before submitting it, also has step by step solutions and is completely free without ads.
I sometimes like it because it does give me the answers correctly but sometimes it doesn't, the only problem and suggestion I have is to give users the ability to change the scale of the graph. Takes the problems and explains them step by step, instead of just showing the solution.
I have te priemium version and its worth it, it is the best math solver ever, i have used this app many time to proof my work. Its so easy to use, I cant even type out how many times math app has helped me with homework. I understand so much more than my teachers have ever taught me.