gradien garis yg melalui A(1, 7) dan B(5, 9)

y - y1 / y2 - y1 = x - x1 / x2 - x1
y - 7 / 9 - 7 = x - 1 / 5 - 1
y - 7 / 2 = x - 1 / 4
2 (x - 1) = 4 (y - 7)
2x - 2 = 4y - 28
2x - 4y = - 28 + 2
2x - 4y = -26

atau
4y = 2x + 26
y = (1/2)x + 26/4