Using exponential function concepts, it is found that the student error is in the subtraction of the day rate, as he forgot to subtract from 100% = 1.
<h3>What is an exponential function?</h3>
A decaying exponential function is modeled by:

In which:
- A(0) is the initial value.
- r is the decay rate, as a decimal.
In this problem, the initial value of the computer is of A(0) = 1500, while it decays at a rate of 15% a year, hence r = 0.15 and the equation is:


Or equivalently, as a sequence:

Hence, it is found that the student error is in the subtraction of the day rate, as he forgot to subtract from 100% = 1.
More can be learned about exponential function concepts at brainly.com/question/25537936