perpendicular y= 1/3 x-2
Find the slope of y = 13·x -2, with respect to x
⇥ 13·x -2
⇥ x3 -2
In y = ax + b, the slope is the coefficient of x: 13
No point is specified: find the family of perpendicular lines
m is the slope of the perpendicular line. The slopes of two perpendicular lines have product -1: 13·m = -1.
⇥Let's solve in ℝ: 13·m = -1
⇥ m3 = -1
⇥ m = -1·3
⇥Solution found: m = -3
The y-intercept b is an arbitrary real number
▶Perpendicular lines:   y = -3x + b