# SAT/ACT problem of the week, September 15, 2016 solution

Hint for process of elimination: Memorize the slope formula: $m=\dfrac{y_2 -y_1}{x_2 -x_1}$, where $m$ is the slope of the line, and $(x_1,y_1)$ and $(x_2,y_2)$ are two points on the line. You should also be able to recognize what lines look like when they have positive versus negative slopes, and large versus small slopes.

The line in the diagram has a positive slope less than 1, making D the only possible choice.

Read on for a full solution.

In the figure above, which of the following expressions can be used to calculate the slope of line $\overline{AB}$?
1. $\dfrac{2-1}{-4+3}$ (check answer)
2. $\dfrac{2+4}{1+3}$ (check answer)
3. $\dfrac{-4+3}{2-1}$ (check answer)
4. $\dfrac{1+3}{2+4}$ (check answer)
5. $\dfrac{1-3}{2-4}$ (check answer)