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

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

Semoga mengerti:)