Answer:
Undefined
Explanation:
The slope of a vertical line does not exist! We can't divide by zero, which is of course why this slope value is "undefined".
We also know that Slope=Tan(θ), for vertical line the θ=90 degree and Tan (90 degree) is undefined .
This relationship is always true: a vertical line will have no slope, and "the slope is undefined" or "the line has no slope" means that the line is vertical.