Question

Draco steals and throws Neville's red ball straight up at 86 feet per second from about 11 feet above the ground. How long does he have until the ball reaches the ground? HINT: Use the function h(t)=−16t2+86t+11, where h(t) is the height of the red ball after t seconds.

Answer 1

So, take their hint, set
−16t2+86t+11 = 0
16t^2 - 86t - 11 = 0

solve using the quadratic equation, reject the negative answer.