The equation of the line x = 3 is a vertical line that passes through all points where the x-coordinate is 3. Since it does not change with respect to y, the slope of this line is undefined.
The slope-intercept form of a line is given by the equation y = mx + b, where m is the slope and b is the y-intercept. For vertical lines, we cannot define a slope (since the rise over run is not a valid calculation, as the run is zero), thus we cannot express a vertical line in the slope-intercept form.
In conclusion, while we can easily identify that x = 3 represents a vertical line, it cannot be represented in slope-intercept form because it lacks a defined slope.