Name: _________________

A farmer was studying the impact of different fertilizers on plant growth.

• Every 3 weeks, he recorded the data in sets of ordered pairs.
• The x-coordinate is the number of weeks at the time of recording.
• The y-coordinate gives the height of the plant in inches.

He recorded the following coordinates for a plant exposed to pollution:

       (3, 2)  (6, 8)   (9, 13)    (12, 17)   (15, 20)

If the pattern continues, at which week should the farmer expect no change in plant height?