Question 51598
{{{x=-3}}} implies that {{{y}}} can have any value.  That implies that the graph is a vertical line going through x=-3.  By definition, vertical lines have undefined slopes.  That can be proven mathematically using {{{m=(y2-y2)/(x2-x1)}}}.  Because the x value never changes, the denominator becomes 0, and division by 0 is undefined; hence, undefined slope.