Amber M. answered 03/21/20
Professor of Physics, Author
Perpendicular Lines mean they have the negative reciprocal slope. This line has slope m = -1 so the perpendicular line has slope m = + 1.
Our point is (9, -4)
Now use point slope form to find the equation: (y - y1) = m(x - x1)
(y - y1) = m(x - x1)
(y - (-4)) = 1(x - 9)
y + 4 = x - 9
y = x - 13