Exercise 4 Page 149

We can calculate the slope by substituting the given points into the Slope Formula.

m = \frac{y _{2} - y _{1}}{x _{2} - x _{1}}

Note that it does not matter which point we choose to use for

(x_{1}, y_{1})

and

(x_{2}, y_{2}),

since the result of using the Slope Formula will be the same.

m = \frac{y _{2} - y _{1}}{x _{2} - x _{1}}

Substitute $(- 3, - 3)$ & $(- 3, - 5)$

m = \frac{- 5 - ( - 3 )}{- 3 - ( - 3 )}

$a - (- b) = a + b$

m = \frac{- 5 + 3}{- 3 + 3}

Add terms

m = \frac{- 2}{0}

In this case, we have a division by zero, which is undefined. This means that the slope is undefined and the given line is vertical.