In the graph given below, find out the slope of y - axis.   

Complete step by step answer:

Slope of y - axis will be undefined.

As, we know that the slope of a line is always tangent of angle made by that line with positive direction of x - axis. 

And as we know that angle made by y - axis text with positive direction of x - axis is $90^ \circ$

And the value of $tan (90^ \circ)$ is undefined.

 So, the slope of y - axis will be undefined.

NOTE: - It should be remembered that slope of any line is always the tangent of angle made by that line with positive direction of x - axis.This will make our problem solving faster.