## Intermediate Algebra (6th Edition)

We can see that value depreciates at the same rate over time by examining the slope of the line in the graph between various points. Recall that the slope formula is $m=\frac{y_{2}-y_{1}}{x_{2}-x_{1}}$. We can plug in the points (0,7), (1,6.5), and (2,6) to this formula (where the y-coordinates are measured in thousands of dollars). $m=\frac{7-6.5}{1-0}=.5$ $m=\frac{6.5-6}{2-1}=.5$ Therefore, this method is called straight-line depreciation because the object depreciates in value at a constant rate over time. In other words, the line in the graph has a constant, linear slope.