y = 3 (or
Lines that are horizontal
have a slope of zero. Horizontal
have "run", but no "rise". The rise/run formula for
slope always yields zero since the rise = 0.
Since the slope is zero, we have
y = mx + b
y = 0•x + 3
y = 3
This equation also describes what is happening to the
y-coordinates on the line. In this case the y-coordinates are always 3.
x = -2 (or
Lines that are vertical have no slope
(it does not exist). Vertical lines have "rise", but no
"run". The rise/run formula for slope always has a
zero denominator and is undefined.
equations for these lines describe what
is happening to the x-coordinates. In this example, the
x-coordinates are always equal to -2.