Active Landfills The number of active landfills in the United States can be modeled...

Active Landfills The number of active landfills in the United States can be modeled as

where x is the number of years after 1989, data from 1 ≤ x ≤ 18.

(Source: Based on data from U.S. Environmental Protection Agency)

a. How many landfills were there in 1990? in 2000?

b. Use output values corresponding to 1990 and 2000 in order to fit a model that can be used as an inverse to the model given.