Answer:
15.5 m
Step-by-step explanation:
Since the ball will reach the maximum height of 18 meters after 1 second, meaning after 1 second it will start to go down. So will expect that the height will be lower than 18 m after 1.5 s.
f(x) = –10x2 + 20x + 8
f(x) = –10(1.5^2) + 20(1.5) + 8
f(x) = 15.5 m