Please help me. and thanks

Find the cosine function that is represented in the graph.

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?

Write as a product: ac^2–ad+c^3–cd–bc^2+bd