persamaan garis melalui titik P(-2,3) dan tegak lurus garis 4x-7y=28adalah

4x -7y = 28
7y = 4x - ...

M = 4/7

M.m = -1
(4/7) . m = -1
m = -7/4

x' , y' = (-2,3)
y-y' = m(x-x')
y-3 = (-7/4)(x+2)
4y-12 = -7x -14
7x+4y +2= 0