the question is asking me to Prove that $d_n$ is constant in the case of compound interest.
What I know so far and have tried is the formula for compound interest is $a(t)=(1+i)^t$ and I think that $d_n$ is possibly supposed to represent the discount maybe. But I there is no $d_n$ in the formula for compound interest so I am confused on how I am supposed to prove this.