In the form of the exponential function:f ( x ) = a · b^x,the base of the function is b.In this case: a = 7,000 ( starting value ) and b = 1 - 0.1 = 0.9f ( x ) = 7,000 · ( 0.9 )^xwhere x represents the number of the years : x = 0, 1, 2, ...Answer: The base is 0.9.