Hello!
Slope-intercept form uses the following formula:
y = mx + b
In this case, "m" represents the slope while "b" represents the y-intercept. The given equation, however, does not contain both variable X and Y. It simply states (x = 4). Consequently, this equation does not have a y-intercept. It gives only the x-value, which is always equal to 4. Therefore, it can be concluded that the line representing (x = 4) is a vertical line intercepting the x-axis at point (4,0).
Vertical lines do not have a slope and are considered to be undefined.
I hope this helps!
