tentukan persamaan garis melalui titik (1,1) dan (-1,2)

[tex] \frac{y-y1}{y2-y1} [/tex] = [tex] \frac{x-x1}{x2-x1} [/tex]
[tex] \frac{y-1}{2-1} [/tex] = [tex] \frac{x-1}{-1-1} [/tex]
[tex] \frac{y-1}{1} = \frac{x-1}{-2} [/tex]
-2 (y-1) = x-1
-2y + 2 = x-1
x + 2y = 3
x + 2y - 3 = 0