The function f (t) = 15,000 (0.86) t models the value in dollars of a used car t years after it is purchased. Is the function an exponential growth function or an exponential decay function?

An exponential function is given by;

f (x) = ba^x

where a is any value greater than 0,

b is the intial value

when a>1 then f (x) is defined as an exponential growth

when a<1 then f (x) is defined as an exponential decay

From the our function;

f (t) = 15000 (0.86) ^t

a=0.86<1

b=15000

since a<1, the function will be an exponential decay.