When the slope of a line is undefined, it indicates that the line is vertical. A vertical line has the same x-coordinate for every point on the line, which means it doesn’t rise or fall as you move along the y-axis.
Given that the x-intercept is 7, this tells us that the line crosses the x-axis at the point (7, 0). Therefore, every point on this line has an x-coordinate of 7 while the y-coordinate can be any real number.
Thus, the equation of the line can be expressed in the form:
x = 7
This equation indicates that regardless of the value of y, x will always equal 7, perfectly representing a vertical line at that x-coordinate.