Some fireworks are fired vertically into the air from the ground at an initial speed of 80 feet per second. The equation for this object's height h at time t seconds after launch is ℎ=−16t2+80t.
Graphing this equation we see that the x intercept, or time when it hits the ground is 5 at 5 seconds. The maximum height it reaches is at 2.5 seconds, 100 feet up in the air. As said in the question, they were launched from the ground so the y intercept is 0. (this is also shown in the equation, no c term)
+149 
