First thing, a line with an undefined slope is a vertical line. That means that every point on the line has the same x-coordinate, and the y-coordinates are all of the real numbers. I'm not sure what you meant by the - for the x-coordinate in the given ordered pair, but let's just say it stands for some real number a. Then the x-intercept would be (a,0). Since every point on the line must have an x-coordinate of a and we don't care what y is, the equation is simply (and you can replace the a with whatever number you meant to put into your given ordered pair)
