Answer
m=0
Work Step by Step
To find the slope of a line, we use the equation m=$\frac{y_{2}-y_{1}}{x_{2}-x_{1}}$. It's given that $x_{1}$=a $x_{2}$=-a $y_{1}$=-b $y_{2}$=-b, so all we need to do is plug the givens into the slope equation.
m=$\frac{-b-(-b)}{-a-a}$=$\frac{0}{-2a}$=0
