how would you describe exponential growth and exponential decay to someone unfamiliar with these phrases?

If 1/√5+1/√5+1=p+q√r , find the values of p, q and r

At the beginning of year 1, carlos invests $600 at an annual compound interest rate of 4%. he makes no deposits to or withdrawals from the account. which explicit formula can be used to find the account's balance at the beginning of year 5? what is, the balance?

Ineed to know how to write question one in mathematical terms