Find the slope of a line perpendicular to the line ax + by = c.

Ax + by = c

by = - ax + c

y = (-a/b) x + c/b ... the slope here is - a/b. A perpendicular line will have a negative reciprocal slope. To find the negative reciprocal, we flip the slope and change the sign. So we have a slope of - a/b ... flip it and it becomes - b/a ... change the sign and it becomes b/a ... so ur perpendicular line will have a slope of b/a <==

The slope would be perpendicular to the second line