Which choice could be the equation of a line perpendicular to the line represented by this equation?

Question

y = 5

for this question, i put this:
y = -1/5x

but, it says i am wrong. how is that? 5 is 5/1, and so the negative reciprocal of 5/1 would be -1/5, right?

Answer 1

You are correct. Maybe they anticipated
(-1/5)*x, or -x/5, or -0.2x, or maybe they are just wrong.

Answer 2

y = 5 or y = 0x + 5
is a horizontal line with slope of 0

Thus a perpendicular line would be a vertical line, which has an undefined slope.

Any vertical line has the form x = k , where k is a constant