Find the perpendicular slope of the line 3X-9Y=15

3x - 9y = 15

-9y = - 3x + 15

y = (-3/-9) x + (-15/9)

y = 1/3x - 5/3 ... slope here is 1/3. A perpendicular line will have a negative reciprocal slope. All that means is " flip " the slope and change the sign.

So our perpendicular slope will be : - 3 (I flipped 1/3 and it became 3/1 or just 3 ... I then changed the sign and it became - 3)

so the perpendicular slope is - 3

According to (-b/a)

So - - 9/3=3

(-b/a) is the equation of the slope