Need to know how to solve quadratic equations? Grab a pen and paper and work along with the video! Remember, you can pause and rewind whenever you want. From Ramanujan to calculus co-creator Gottfried Leibniz, many of the world's best and brightest mathematical minds have belonged to autodidacts. And, thanks to the Internet, it's easier than ever to follow in their footsteps (or just finish your homework or study for that next big test).