Undefined slope is when a line becomes vertical. Vertical lines have undefined slope because if we attempt to find the slope using formula, the denominator will become 0 which is undefined.
Next, the equation of a vertical line is x = a where a is any real numbers.
Since the line is vertical, for any a-value would have same y-value which is all real numbers.
However since the graph passes through x = 3. For x = 3 has y-value as set of all real numbers.
Answer
The equation for a line that has undefined slope and passes through (3,5) is x=3
