When a line has an undefined slope, it means that it is a vertical line. Vertical lines are written in the following form:
For any vertical line, the x-coordinate is constant. This means that for any point that falls on the line, the x-coordinate will always be the same.
If we're given that the line passes through the point (4,-2), this means that the x-coordinate for every piont this line passes through is 4.
In other words, the x-intercept of this line is 4.
[tex]x=4[/tex]
[tex]x=4[/tex]