We have the following equation: h (t) = - 16t ^ 2 + 161t + 128 We substitute the value of h (t) = 170: 170 = -16t ^ 2 + 161t + 128 We rewrite the equation: -16t ^ 2 + 161t + 128 - 170 = 0 -16t ^ 2 + 161t - 42 = 0 We look for the roots of the equation: t1 = (161/32) + root (23233) / 32 t2 = (161/32) - root (23233) / 32 Answer: The object is 170 feet off the ground at the following times: t1 = (161/32) + root (23233) / 32 t2 = (161/32) - root (23233) / 32
