Hello. I was hoping someone could help me with this problem as it relates to polynomial functions.

A projectile is thrown upward so that its distance above the ground after t seconds is given by the function h(t) = - 16t^{2}+ 576t. After how many seconds does the projectile take to reach its maximum height?

It would be nice if you could give me a full explanation as I truly want to learn how to do this. Thank you so much guys.