No matter how chaotic the train station at rush hour might seem, there’s likely more order than you think in that crowd. It’s long been observed that in a dense crowd with people headed in opposite ...

Horizontal lines run left to right, parallel to the horizon, with slope 0 and equation y = k. Vertical lines run top to bottom, perpendicular to the horizon, with undefined slope and equation x = k.

This jingle has helped generations of algebra students recall the quadratic formula that solves every equation of the form $latex ax^2+bx+c=0$. The formula is as ...