## Precalculus (6th Edition) Blitzer

$\dfrac{y_2-y_1}{x_2-x_1}$
RECALL: The slope $m$ of a line can be found using the formula: $m=\dfrac{y_2-y_1}{x_2-x_1}$ Thus, the missing expression in the given statement is: $\dfrac{y_2-y_1}{x_2-x_1}$