Write the equation of the line, in slope-intercept
form, that contains the points: (7,4) and (-8,4)

Use the slope formula:

     y2 - y1
m = —————————
     x2 - x1

where (x1, y1) = (7, 4) and (x2, y2) = (-8, 4)

     (4) - (4)     0     
m = ——————————— = ———— = 0
    (-8) - (7)    -15      

Now substitute in the point slope formula:

   y - y1 = m(x - x1)

   y - 4 = 0(x - 7)

   y - 4 = 0x - 0

       y = 0x + 4

It's normally written just y = 4, but with the
0x in there it is in the form

      y = mx + b

where the slope is 0 and the y-intercept is the
point (0, b) which is (0, 4).  The line is a horizontal
line 4 units above the x-axis:



Edwin