Question 908390
A fireworks shell is shot straight up with an initial velocity of 80 feet per second. Its height s after t seconds is given by the equation 
s = 80t − 16t2.
If the shell is designed to explode when it reaches its maximum height, how long after being fired, and at what height, will the fireworks appear in the sky?
***
s=80t-16t^2
s=-16t^2+80t
complete the square
s=-16(t^2-5t+25/4)+100
s=-16(t-2.5)^2+100
how long after being fired, and at what height, will the fireworks appear in the sky? 2.5 sec at a height of 100 ft