[填空题]
A cannon-ball is fired from the t bh/7cryg/r f2op of adij(2s 3mvqxme/- 7rh tower. The height, ℎh, in metres, of the cannon-ball above the ground is modem-r x v3hjs q/ed7m(i2lled by the function
h(t)=−2$t^2$+20t+8,t≥0,where t is the time, in seconds, since the moment the cannon-ball was fired.
1.Write down the height of the tower. h = m
2.Calculate the height of the cannon-ball 5 seconds after it was fired.
The cannon-ball hits its target on the ground n seconds after it was fired. h = m
3.Find the value of n. n ≈
4.Find h′(t). h′(t) = at +b a = b =
5.Calculate the maximum height reached by the cannon-ball, and write down the corresponding time t.
6.Determine the total time the cannon ball was above the height of the tower. t = seconds