Use the rise over run formula to find the slope:
[tex] \frac{y2-y1}{x2-x1}[/tex]
[tex] \frac{-1 - 7}{4-2} = \frac{-8}{2} = -4[/tex]
Find the y-intercept of the line by multiplying the slope by the distance between x = 0 and a point. We'll use (2,7) to find the y-intercept.
0 - 2 = -2
-2(-4) + 7 = 15
The new point on the line is (0,15). Since x = 0, 15 is your y-intercept.
Plug in your slope and y-intercept into the equation:
[tex]y = mx + b[/tex]
Answer:
[tex]y = -4x + 15[/tex]
