persamaan garis lurus dari (1,3) dan (8,-5)

y-y1 / y2-y1 = x-x1/x2-x1
y-3 / -5-3 = x-1/8-1
y-3/-8 = x-1/7
7y-21 = -8x+8
7y+8x-29= 0
y = 8/7 x - 29/7