Given two points: A(x₁,y₁) and B(x₂,y₂), the slope of the line that passes through these points will be: m=(y₂-y₁)/(x₂-x₁)
If we take two points of this line (3,0) and (3,1) and calculate the slope, we have: m=(1-0)(0/0)=1/0 (any number divided by zero gives an indetermined value).
