Learn how to write the equation of a line that is perpendicular to a given line. The equation of a line is such that its highest exponent on its variable(s) is 1. (i.e. there are no exponents in its ...

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.