persamaan garis melalui titik (5,6) dan (7,12)

(y - y1) / (y2 - y1) = (x - x1) / (x2 - x1)
(y - 6) / (12 - 6) = (x - 5) / (7 - 5)
(y - 6) / 6 = (x - 5) / 2
2(y - 6) = 6 (x - 5)
2y - 12 = 6x - 30
2y = 6x - 30 + 12
2y = 6x - 18
y = 3x - 9