Question 201420
First, if a line has an "undefined " slope, then the line is vertical, thus it has no y-intercept (unless, of course, the line is right on the y-axis).
Starting with the slope-intercept form of the equation for a line, (y = mx+b), you know that the y-intercept (b) will be zero.
So the equation of the vertical line that passes through the point (10, -5) is:
{{{highlight(x = 10)}}}
To graph this equation, you can use any point that has an x-coordinate of 10.  The y-coordinate can be any number you choose, and you can see, when you graph this line, that it is vertical (slope is undefined) and that it passes through the point (10, -5).