Why do you use linear extrapolation?
Linear extrapolation is used to answer certain questions like:
(insert name here) and (insert name here) start a (insert business thingy here) business and start with $2,000 per year. They get more customers each year. For each they they continue to work, they gain $2,000 more than the last year, and then they take away the cost of materials, $500.
The equation is:
Pretend that there is a graph that lasts 20 years. Now, figure out how much money they will have after 30 years.
By the way, that's: