안녕하세요 이연욱 샘입니다.
The exact value of compound interest formula considering the inflation rate in decimal is A=P (1+r)^t / ((1+i)^t), where P is the initial amount, r is the interest rate in decimal, and i is the inflation rate in decimal.
하지만, 저의 강의시간에 설명한 A=P (1+r-i)^t 은 approximation of A=P (1+r)^t / ((1+i)^t). When the difference between r and i is small, P (1+r-i)^t is very close to P (1+r)^t / ((1+i)^t).
따라서, 학교에서 exact value of compound intereset formula를 사용한다면, A=P (1+r)^t / ((1+i)^t)를 사용하는 것이 맞습니다.
감사합니다.