(x2-x1)(y-y1)=(y2-y1)(x-x1),(u2-u1)(y-v1)=(v2-v1)(x-u1) for x, y

Uh oh! Wolfram|Alpha doesn't run without JavaScript.

Please enable JavaScript. If you don't know how, you can find instructionshere.Once you've done that, refresh this page to start using Wolfram|Alpha.