The function is:
f(x)=190× # 0.99 # ^x
Since xrepresents the number of years since 2003:
2012 # x=9
2015 # x=12
The average rate of change from 2012 to 2015 is:
(f(12)-f(9))/(12-9)
First, find f(9):
f(9)=190× # 0.99 # ^9
f(9)#173.59
Now find f(12):
f(12)=190× # 0.99 # ^12
f(12)#168.37
Now calculate the average rate of change:
(168.37-173.59)/(12-9)
=(-5.22)/3
#-1.74
Rounded to the nearest whole number:
-2
The negative sign means the number of subscribers is decreasing.
So the correct interpretation is:
" The number of subscribers decreases at an average rate of about 2 subscribers per year. "