The number of asthma sufferers in the world was about 84 million in 1990 and 300 million in 2009. Let N represent the number of asthma sufferers (in millions) worldwide t years after 1990.
Write N as a linear function of t. What is the slope? What does it tell you about asthma sufferers?
Write N as an exponential function of t. What is the growth factor? What does it tell you about asthma sufferers?