Write the equation of the line passing through
(3, –7) and (–6, –7).
Use the slope formula:
y2 - y1
m = —————————
x2 - x1
where (x1, y1) = (3, -7) and (x2, y2) = (-6, -7)
(-7) - (-7) -7 + 7 0
m = ————————————— = ———————— = ———— = 0
(-6) - (3) -6 - 3 -9
Now substitute in the point slope formula:
y - y1 = m(x - x1)
y - (-7) = (0)( x - (-6) )
y + 7 = 0
y = -7
which is a horizontal line 7 units below
and parallel to the x-axis.
You could have just plotted the points and
drawn a line through them,
and observed that every point on the line
has the y-value -7, and just immediately
written that y always = -7, or y = -7.
Edwin
