[问答题]
Jessica hits a tennis serve and the path of the ball can be modelled by the function
h(d)=2+d−$\frac{d^2}{5}$
where h is the height above ground level in meters, and d is the horizontal distance the tennis ball travels, also in meters.
1.Find the horizontal distance travelled by the ball when it hits the ground.
2.Find the maximum height the ball reaches.
On her next serve, Jessica hits the ball harder and flatter, so that the ball reaches the same height as the previous serve, but travels twice as far.
3.Determine a new height function, $h_2$, that describes this trajectory.
