Is a exponent determined by the amount of zeros in the number?

Use sigma notation to represent the following series for 9 terms.

Rationalize the denominator- 12x/√x-10

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?