Exercise 20 Page 160

To write the equation of a line perpendicular to the given equation, we first need to determine its slope.

The Perpendicular Line's Slope

Two lines are perpendicular when their slopes are negative reciprocals. This means that the product of a given slope and the slope of a line perpendicular to it will be $\text{-}1.$ For any equation written in slope-intercept form, $y=mx+b,$ we can identify its slope as the value of $m.$ Since the given equation is not written in slope-intercept form, we will have to rewrite it before identifying the slope.