Point $A$ has coordinates $(-13,-23)$ and point $B$ has coordinates $(-33,-43)$. What is the slope of a line that is perpendicular to the line segment $A B$ ?
The slope of $A B$ is $\frac{-43-(-23)}{-33-(-13)}=\frac{-20}{-20}=1$.

Since $A B$ is neither horizontal nor vertical, the slope of a line perpendicular to it is the negative of the reciprocal of 1 , or $\frac{-1}{1}=-1$.

ANSWER: -1