Suatu garis melalui titik p (-2,3)dan Q (4,5) adalah

y-y1/y2-y1 = x-x1/x2-x1
y-3/4-3 = x-(-2)/1-(-2)
y-3/1 = x+2/3
3(y-3) = x+2
3y-9 = x+2
3y = x+2+9
3y = x+11
3y-x = 11