Need advice. How relearn what Ive forgotten?

Question

The last time I studied mathematics and algebra was six years ago. I've since forgotten everything except quadratic equations, trigonometric functions and other things at the same level. Now I want to relearn all this: combinatorics, linear algebra, probability theory. I'm looking at articles in wikipedia, and don't understand anything except the basics. Trying to understand a topic, I dig deeper and deeper into wikipedia and after a while, I can't even remember where I started.

So my question: what things I must learn for first steps?

Answer 1

If you need the basics, perhaps a free MOOC (massive open online course) and even Khan Academy might me a nice option to go:

https://www.coursera.org/category/math

http://www.khanacademy.org/

Answer 2

Wikipedia can be useful (sometimes very useful) for filling gaps in knowledge when you already have some background. But it is pretty useless as a place to begin (it often isn't even very good at giving pointers to good textbooks).

We live in a golden age for maths textbooks at different levels: there are a lot of quite wonderful books out there, written by experienced teachers, and often polished over a number of editions. Get yourself to a good library and see what is available that meets your needs and interests. Different books even at the same level will suit different readers, so find a book that looks as if it will work for you. Then borrow it, read it slowly and carefully, doing some of the exercises as you go along.