Aball is released at a height of 27 inches to roll inside a half-cylinder. it rolls
to a height of 9 inches on the other side of the cylinder on roll 1. each time it
rolls up a side of the cylinder, the ball reaches a point th
high as it
had reached on the other side.
this explicit formula models the height of the ball, in inches, the nth time it
rolls up a side of the cylinder.
how high does the ball roll on its 4th time up the cylinder's side?