Determine equation of a line passing through a point (5,-3) with and undefined slope

Slope is calculate using the following equation:
slope = (y2-y1) / (x2-x1)
since the slope is undefined, therefore, the denominator is equal to zero, which means that x2 = x1.

Based on this, the only curves with undefined slopes are the curves with equation: x = constant

Therefore, equation of a line passing through a point (5,-3) with and undefined slope is x = 5