Final answer:
To represent the relationship between the resale value of the copy machine and the number of years since the purchase, you can use the exponential function y = 11500 * (1 - 0.18)^t.
Step-by-step explanation:
To write an exponential function showing the relationship between y and t, we can use the formula for exponential decay. In this case, the resale value is decreasing by 18% each year. So, the function can be written as:
y = 11500 * (1 - 0.18)^t
Here, y represents the resale value of the copy machine in dollars, and t represents the number of years since the purchase. The base of the exponential function is (1 - 0.18) because the value is decreasing by 18% each year. This formula can be used to calculate the resale value of the copy machine for any given number of years since the purchase.