If r = x y 1 1 0 g and A = 0 1 f g f c show that r^T Ar = 0 is the equation of the circle in R^2 with centre (−g, −f) and radius square root(g^2 + f^2 − c).

Samuel deposited money in an account that’s pays an annual simple interest rate at 3.5%. at the end of 5 years, samuel earns $2625.00 in interest. how much money did he deposit in the account?