Tentukan persamaan garis melalui titik 2,1 dan 5,2

(y-y' /y''-y') = (x-x' / x''-x')
(y-1 / 2-1) = (x-2 / 5-2)
y-1 / 1 = x-2 / 3
y-1 = x-2 / 3
3(y-1) = x-2
3y-3 = x-2
3y = x-2+3
3y = x+1
x-3y+1 = 0