At the beginning of a basketball game, the referee tosses the ball vertically into the air. Its height, h, in feet after t seconds is given by h(t) = -16t2 + 24t +5. During what time interval (to the nearest tenth of a second) is the height of the ball greater than 9 feet?

Question

At the beginning of a basketball game, the referee tosses the ball vertically into the air.  Its height, h, in feet after t seconds is given by h(t) = -16t2 + 24t +5.  During what time interval (to the nearest tenth of a second) is the height of the ball greater than 9 feet?

Steve · Answer

-16t^2 + 24t + 5 > 9 16t^2 - 24t + 4 < 0 3-√5 < 4t < 3+√5 0.2 < t < 1.3