Question

consider the line y=-5/4x+4. What is the slope of a line parallel to this line? What is the slope of a line perpendicular to this line?

Answer 1

m = 4/5 for the perpendicular line

m = -5/4 for the parallel line

y = -5/4x + 3

for the line above, m = -5/4

The line parallel to this line would have exactly the same slope m =  -5/4

The line perpendicular to this line would have a  slope equal the inverse with the opposite sign  

m = -5/4

So m = (1/(5/4)) is the slope of the m for the perpendicular line

m = 4/5