When a rock is dropped in a body of water, it will produce ripples of water made up of concentric expanding circles. Suppose the radii of the circles expand at 3 inches per second. 1. Write an equation for the circle 10 seconds after the rock is dropped in the pond. Assume that the point where the rock is dropped is the origin. 2. One concentric circle is given by the equation, 2 2 x y + = 225 . How many seconds, after the rock is dropped, does it take for the circle to have this equation?