## Elementary and Intermediate Algebra: Concepts & Applications (6th Edition)

RECALL: (1) The slope $m$ of a line can be found using the formula $m=\dfrac{y_2-y_1}{x_2-x_1}$ where $(x_1, y_1)$ and $(x_2, y_2)$ are points on the line. (2) A vertical line has an undefined slope. Thus, the formula for slope in (1) above only works when the points are not from a vertical line. Therefore, the given statement is true.