Question 236963
Let  m= {18-(-6)}/ { 9- 3} = 24 /6 = 4
.
m= (y2-y1)/(x2-x1)
.
using  the  point  slope  eqn  with  extreme  coordinate  pairs
.
y-y1 = m (x-x1)
.
y-18 = 4(x-9)
.
y-18 = 4x -36,,,,,,,subtracting  y,, and  adding  36  to  both  sides
.
18 = 4x -y
.
.
checking,   y=4x -18,,,,,,all  coordinates  match  ,,,,,ok