If the graph of the line y = ax + b passes through the points (4,5) and (8,-17), what is a - b?
a = the slope = [ -17-5 ] / [ 8 -4] = -22 / 4 = -11/2
b = the y intercept
So using (4,5) the equation of the line is
y = ( -11/2)(x - 4) + 5
y = (-11/2)x + 22 + 5
y = (-11/2)x + 27
b = 27
a - b =
-11/2 -27 =
-11/2 - 54/2 =
- 65 / 2
