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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?