Persamaan garis lurus yang melalui titik(2.-4)dan(-1.3) adalah

m = (y2 - y1) : (x2 - x1)
m = 3 + 4
       ------
       -1 -2
m = 7/-3

y = mx + c
-4 = 7/-3 (2) + c
-4 = -14/3 + c
-4 + 14/3 = c
-12/3 + 14/3 = c
2/3 = c

y = 7/-3x + 2/3
Kalikan persamaan dengan 3
3y = -7x + 2
-7x - 3y + 2 = 0

y-y1/y2-y1 = x-x1/x2-x1
=y-(-4)/3-(-4) = x-2/-1-2
=y+4/7 = x-2/-3
=-3y-12 = 7x-14
=-7x-3y-12+14=0
=-7x-3y+2=0