Question 122640
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Discussion
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The set of points that forms the line {{{x=-7}}} 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 {{{(y[1]-y[2])/(x[1]-x[2])}}}.  But in the equation
{{{x=-7}}} 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.  
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