Explanation:
a line with undefined slope is a vertical line, because x does not change on this line at all, and therefore the shoe is y/0.
a vertical line is parallel to the y-axis.
and to go through the given point, it has to use the x- coordinate.
so, the equation is
x = -5
that's really it.
this is the line of all points with the x-coordinate = -5. any value for y is valid.