The numbers y of commercial banks in the United States from

The numbers y of commercial banks in the United States from 1999 through 2009 can be modeled by y = 13107 - 2077.6 Int, 9 lessthanorequalto t lessthanorequalto 19 Where t represents the year, with t = 9 corresponding to 1999. In what year were there about 7100 commercial banks?

Solution

solution:

y=13107-2077.6lnt 9<t<19

where t=9 means 1999

for y=7100

7100=13107-2077.6lnt

-6007=-2077.6ln(t)

2.891317= ln(t)

t=e^2.891317

= 18.01 or t=18

as t=9 cooresponds to 1999

so t=18 cooresponds to 2008

hence in 2008 7100 commercial banks