Due to the poor economy, a real estate investor lost 120 thousand dollars in 2008. Let the ordered pair (2008, -120) represent this relationship. The

investor did better in 2010 by earning 350 thousand dollars. Let the ordered

pair (2010, 350) represent this relationship. Ruben was asked to calculate the

average rate of change for the investor's earnings from 2008 to 2010.

To solve this, Ruben uses the slope formula to calculate the rate of change

between 2008, -120) and (2010, 350). The student's work is shown below:

(a) Using complete sentences, explain the two mathematical errors in the

student's reasoning.

(b) Calculate the correct rate of change between (2008, -120) and (2010,

350)