The line is tilted downward (meaning that the line has a negative slope) to model the object's depreciation.
Work Step by Step
The line has a negative slope, meaning that the y-coordinate decreases as the x-coordinate increases. This accurately models the object's depreciation in value. As the x-coordinate increases, the y-coordinate (which measures the object's value at a given time) decreases. In other words, after each year, the object loses more and more value.