In this case, we'll have to carry out several steps to find the solution.
Step 01:
Data:
lines
Step 02:
perpendicular lines:
line 1 and line 2 are perpendiculars:
line 1:
slope = m
line 2:
slope = m'
The relation between the slopes is:

The slopes of two perpendicular lines are negative reciprocals of each other.
The answer is:
The relation between the slopes is: m' = - 1 / m
The slopes of two perpendicular lines are negative reciprocals of each other.