persamaan garis yang melalui titik A(-1, 0)dan B(3,-8) adalah

(y - y1) / (y2 - y1) = (x - x1) / (x2 - x1)
(y - 0) / (-8 - 0) = (x + 1) / (3 + 1)
y / (-8) = (x + 1) / 4
4y = - 8(x + 1)
4y = - 8x - 8
y = - 2x - 2

[tex]\frac{X- Xa}{Xb-Xa} = \frac{Y - Ya}{Yb-Ya} [/tex]
[tex] \frac{x+1}{4} = \frac{y}{-8} [/tex]
4y = -8x-8
8x + 4y = -8
4x+2y = -4