persamaan garis yg melalui titik (3,-2) dan (4,1) adalah

(3,-2) = (x1,y1)
(4,1) = (x2,y2)

y - y1 / y2 - y1 = x - x1 / x2 - x1
y + 2 / 1 + 2 = x - 3 / 4 - 3
y + 2 / 3 = x - 3 / 1
y + 2 = 3(x - 3)
y + 2 = 3x - 9
y = 3x - 11

(3,-2) dan (4,1)
x1 = 3 x2 = 4
y1 = -2 y2 = 1

y - y1/y2-y1 = x - x1/x2 - x1
y - (-2)/1 - (-2) = x - 3/4 - 3
y + 2 / 1 + 2 = x - 3/4 - 3
y + 2/3 = x - 3/1
kali silang
1(y + 2) = 3(x - 3)
y + 2 = 3x - 9
y = 3x - 9 - 2
y = 3x - 11
3x - y - 11 = 0
3x - y = 11