persamaan garis melalui titik (4,3) dan (1,-1) adalah...

(y-y1)/(y2-y1) = (x-x1)/(x2-x1)
(y-3)/(-1-3) = (x-4)/(1-4)
y-3/-4 = x-4/-3
kalikan silang
-3y+9 = -4x+16
4x-3y = 7

x1= 4
y1=3
x2=1
y2=-1
jawab:
y-y1 = x -x1
___ ___
y2-y1 = x2-x1

-> y-3 = x -4
___ ___
-1-3 1-4

y-3*-3 = x-4 * -4
y9 = x16
xy = 16/9
xy = 1.77