Bryan L. answered 11/02/20
Math and Physics Tutor for All Ages
Perpendicular is the "opposite Reciprocal."
Opposite means that you change the sign (positive to negative, or vice versa)
Reciprocal means you put 1 over the number. So the Reciprocal of 2 is 1/2. The reciprocal of 1/9 is 1/(1/9) which is 9.
So, the opposite reciprocal of 8 is -1/8. Which is the going to be the perpendicular slope.