#9: First, find the equation of the line through the points (-1, -4) and (6,10).
10-(-4)
Here's the slope: m = ---------- = 14/7 = 2
6-(-1)
Since we want the y-intercept, start with the slope-intercept form: y = mx + b.
Borrowing x=6 and y=10 from the 2nd point, we get
10 = 2(6) + b. Then b = 10-12, or b = -2.
The equation of the line thru the given points is y = 2x - 2.
Check: Does (-1, -4) satisfy this equation? -4 = 2(-1) -2 yes.