Find a if the point (-6,a) is on the line that passes through (-1,7) and (3,-2).
The slope through (-1,7) and (3,-2) is (3 - (-1))/(2 - 7) = 4/5. Then by point-slope form, the equation of the line is y + 1 = 4/5(x - 7). We want the value of y when x = -6, so a + 1 = 4/5(-6 - 7). The answer is a = -57/5.
