is a vertical line. The x-coordinate of any point on this line is -8. So if you tried to calculate the slope you would have:
. The y-coordinates can be anything you like, but the denominator still becomes zero, and division by zero makes the quantity undefined.
As to the y-intercept, ask yourself, "Which point on this line has an x-coordinate of zero?" The answer is none of them, since all of the points on this line have an x-coordinate of -8.
Perhaps it might help if you remember that a line on a graph is actually a set of points with an infinite number of elements. The equation for a line establishes the relationship between the x and y coordinates for each of the points in the set. So when you write x = -8, you are actually saying this is a set of all possible points such that x = -8. That set would consist of all possible points that have -8 as an x-coordinate, and that the points would differ only in the value of the y-coordinate. There are an infinite number of points because there are an infinite number of values for y.
