Discussion
The set of points that forms the line
is every point that has an
x-coordinate of -7 paired with every possible real number value for y. The
slope of a line is given by
. But in the equation
the x-coordinate for any point on the line is -7. That means that
the denominator of the slope calculation is 0, therefore the slope is
undefined. Since x = -7 no matter what y is, this line never crosses the
y-axis. There is no y-intercept because the line is vertical and therefore
parallel to the y-axis.