persamaan garis yang melalui titik (-3,6) dan (1,4) adalah

x1 = -3
y1 = 6
x2 = 1
y2 = 4

Rumus 
y - y1/ y2 - y1 = x - x1 / x2 - x1

y - 6 / 4 - 6 = x + 3 / 1 + 3
y - 6 / -2      = x + 3 / 4 

4( y - 6 ) = -2( x + 3 ) 
4y - 24   = -2x - 6 
4y +  2x   = -6 + 24
4y +  2x   = 18 
2y +  x     = 9 

x1 = -3
x2 = 1
y1 = 6
y2 = 4
[tex] \frac{y - y_1}{y_2-y_1}= \frac{x - x_1}{x_2-x_1} [/tex]

= [tex] \frac{y - 6}{4-6}= \frac{x +3}{1+3} [/tex]

= [tex] \frac{y - 6}{-2}= \frac{x +3}{4} [/tex]

= 4 (y - 6) = - 2 (x + 3)
= 4y - 24 = -2x -6
= 4y = -2x -6 + 24
= 4y = -2x + 18 atau 2y = -x + 9