Question

Is it possible to teach myself higher math if I know differential equations, linear algebra and Calc 3?

Answer 1

Yes but it's pretty tough starting out because proof base, rigorous, math is very different from your previous math courses. It's generally a good idea to take some classes to introduce you to proof based math and then once you've gotten the hang out if you can self teach. That being said it's not impossible by any means. Just more difficult

Answer 2

To learn all you need is a book and to do some problems. But it's pretty rough if you don't have someone to ask questions of. Or to review your proofs.