A projectile is thrown upward so that its distance above the ground after t sec is given by h(t)=-11t^2+396t. After how many seconds does it reach its max heigh

Question

Math help please

Answer 1

you can find the maximum height by plotting this quadratic function, or

by finding the derivative and setting it equal to zero.  

h'(t) = -22t+396 = 0

t = 18s