Question

What is the slope of the line x=-5

Answer 1

Undefined - this line is a vertical line, so therefore would have an undefined slope

Answer 2

x= - 5
It is a vertical line,
all values of x are the same, so when you write a formula for the slope
m=Δy/Δx,
you see that Δx=x2-x1=0,
We need to divide by 0,
so a slope of any vertical line is undefined.