I am not sure how helpful this would be to you. I just started this course: https://www.coursera.org/learn/learning-how-to-learn

This seems to be very popular and highly recommended in Reddit. She briefly talks about how she was scared off of maths at one point in her life and later went on to get a phd. She also has a book on the same topic. Note that the course is not math specific.

I’d call what you want to do “teach yourself maths as a foreign language”. It can very much be done because I did it.

If I could do it all again, I’d start with an old school Calculus course. E.g “Calculus” by Binmore . It’s a decent and well explained introduction to Calculus and Linear Algebra and it’s useful maths. You have to get a hang of thinking in maths and doing maths you find boring.

From here it depends on what you want to do. There’s more maths out there than there is time so you need goals.

Go to expii.com and start doing a module to test where you're at. You do exercises and if you don't get something, it shows you a 5min lesson. It's a startup by the guy who coaches the US olympiad team. When you're done find some introductory text that goes about proving things, such as Hoffman & Kunze Linear Algebra or Concrete Math by Knuth et all. Concrete Math is accessible to a motivated highschool student. You have Math stackexchange to ask questions or hire a tutor from a local university to walk you through some of the proofs at a coffee shop on a Sunday afternoon. I paid a grad student to review my terrible attempts at proofs when I started going through the exercises of these intro books, highly recommend you do this too.

Math is huge so how you approach this will depend a lot on your starting point and your goal.

Which branch of math are you interested in?

Do you need it for something specific to your career or is it just a hobby?

What's you current level - are you comfortable with high-school level algebra, trigonometry, calculus?

In any case, I second the recommendation for Khan Academy as a good starting point - not only for the range of content and Sal's silky voice, but also for their approach to learning: you get to practice topics until you "master" them instead of just watching/reading, maybe taking a test and then moving on to the next topic.

Khan Academy has everything from basic addition to multivariable calculus and linear algebra. All free and online.

https://www.khanacademy.org/

If you google “3blue1brown” you’ll get a youtube channel that has good visuals for building your intuition before deeply learning about a topic.

See previous discussion of this topic:

https://news.ycombinator.com/item?id=18939913

If I were you, I would better find a subject that interests me ( for example AI or statistics ) and learn the math I need to understand to play with it

It heavily depends, whether you want to use math as a tool or focus on math because math fascinates you.

A huge part of math is learning how things work, how to look at things, when there’s actually an easier way to do things than that one formula you just learned. Even if a book can perfectly teach you this, you still lose a lot of perspective.

If you get a teacher, or at the very least someone who is helping you, or even just learning alongside you, you’ll learn far more efficiently, as what the other person thinks may be put in a phrasing, or use a tactic, or have some reasoning, the list goes on, that you could never have come up with on your own. Even if you’re smarter than Newton - well - Newton didn’t get to where he got without a little help throughout his life.

HOWEVER.

That’s not to say it’s impossible. If you really have a love for mathematics, there a loads of ways to learn more math. If you’re looking just to get some random math knowledge, then roaming YouTube is actually a pretty effective method of gaining some fun knowledge. Those guys are average joes just like you and I. They always have something fun to get your hands on.

If, however, you’re looking for a specific subject, or something that would otherwise replace a class, then get the best textbook you can find and get a tutor. Maybe you’ll be fine on your own, but two heads are still better than one, especially with education. Math builds on itself. If you just barely scrape by in Algebra, Calculus isn’t going to be fun. You need to have a pretty good understanding of everything. That’s why its so hard.

One last tip: pace yourself. If you think you’ve got a topic after reading it and working on a couple of problems, still take a day on it. You’ll find something you missed, find a shortcut, or something, and it’ll make the next topic just that much easier. And again, that’ll carry on.