How do you learn how to write linear equations

Through non-collinear points there is exactly one plane.

Which is the focus of a parabola with equation y2=4x

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?