Build the equation according to y = mx + b.
The slope (m above) is found by examination
of (-4,-1) and (2,8). Take m as the ratio of
the difference of the y-coordinates to the
difference of the x-coordinates.
That is, m = (8 − -1) ÷ (2 − -4) or 9/6 or 1.5.
Then y = mx + b becomes y = 1.5x + b.
Use (2,8) to write y = 1.5x + b as
8 = 1.5(2) + b.
Find b (the y-coordinate of the point where
the line sought intersects the y-axis) as 8 − 1.5(2)
or 8 − 3 equal to 5.
Then complete the equation of the line as y = 1.5x + 5.
Note that 8 does equal 1.5 times 2 plus 5 and
-1 does equal 1.5 times -4 plus 5.
