Answer: C. y=-5x-8
Step-by-step explanation
x-5y=-40 is of the form Ax+By = C which is known as standard form.
A = 1, B = -5, C = -40
The slope is found by the formula: m = -A/B where B is nonzero.
The slope in this case is: m = -A/B = -1/(-5) = 1/5
Flip the fraction and flip the sign to get the perpendicular slope. In other words, take the negative reciprocal. We go from 1/5 to -5/1 aka -5.
The perpendicular slope is -5.
Of the answer choices, only choice C has slope -5.
Perpendicular slopes multiply to -1 when neither line is vertical nor horizontal. So (1/5)*(-5) = -1.