An object is fired vertically upward with an initial speed of 68.6 meters per second. After t seconds, the height is shown by y = 4.9t^ + 68.6 t meters. Given that this object has an initial speed of 68.6 m/s, what is the maximum height it will reach?

Answer 1

if height y is

y= 4.9t^2+ 68.6t, it is a very odd object, gravity is not going to ever pull it downward. I suggest this is more likely in the real world:

y= - 4.9t^2+68.6t

so y max can be found when
y'=0=-9.8t+68.6 and solve that for t, the time at the max.
then put that t into the y equation.