Question 457645
s=-4.9t2+4.9t+9.8
4.9t2-4.9t-9.8=0
t2-t-2=0
(t+1)(t-2)=0
t=2 or -1
Throwing out the negative answer, the object will hit the ground in 2 seconds.
2.8<-4.9t2+4.9t+9.8
0<-4.9t2+4.9t+7
*[invoke quadratic "x", -4.9, 4.9, 7 ]
The area in the upper right quadrant in your graph represents the time the object is above 2.8 meters..