A student attempts to determine the focal length of a mirror through graphical analysis. They make a series of observations by changing the position of an object and measuring the position of the corresponding focused image. When they graph their data to create a linear relationship, they obtain the following graph.

Observations of a Converging Mirror 4.5 4 3.5 3 2.5 1/dj (m-1) 1.5 0.5 0.5 1.5 2 2.5 3.5 4 4.5 1/do (m-1)