Do the functions have the same concavity? f(x)=-x^2+40x+120

Asphere has a diameter of 10 in. what is the volume of the sphere?

10 ! a train starts from grand city and travels toward belleville 388 miles away. at the same time, a train starts from belleville and runs at the rate of 47 miles per hour toward grand city. they pass each other 4 hours later. find the rate of the train from grand city.

Can someone me with #s 8, 9, and 11. with just one of the three also works. prove using only trig identities.