Question 1191997
h(t)=-5t^2+30t
vertex for this negative quadratic is where t=-b/2a=-30/-10 or t=3 seconds at highest point.
the height is -45+90=45 m
It will be in the air 6 seconds, since this is symmetric
It will hit the ground in 6 seconds. 
{{{graph(300,300,-5,10,-25,50,30x-5x^2)}}}