求解一道AP微积分应用题!

题目

求解一道AP微积分应用题!
A ball is thrown upward from the top of a building feet tall.The height of the ball is described by the function y(t),=-16t^2+14t+250.where t is in seconds and t=0 corresponds to the moment the ball is thrown.
(1)Determine for which value of t the ball reaches the maximum height and determine this maximum height.
(2)
Determine when the ball reaches the ground.
(3)With what velocity does the ball hit the ground?

答案

（1）第一问求t为何值时球达到最大高度 y'(t)=-32t+14 令其等于0 解得t=7/16 再带入 y(t),=-16t^2+14t+250 解得最大高度（2）第二问球什么时候落地令y(t),=-16t^2+14t+250=0 解得的t（取正的那个）就是（3）问球落地...