perpendicular x+y=-1
⇥Let's solve in ℝ: x + y = -1
⇥ y = -1 -x
⇥Solution found: y = -x -1
The slope-intercept form is y = mx + b: the slope is -1 and the y-intercept is -1
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: -1·m = -1.
⇥Let's solve in ℝ: -1·m = -1
⇥ -m = -1
⇥Solution found: m = 1
The y-intercept b is an arbitrary real number
▶Perpendicular lines:   y = x + b