Question 1187125
I assume this should be h(t)=-4.9t^2+49t + 1.5
this is a negative quadratic so the vertex t=-b/2a is the time at maximum, and that is -49/-9.8 or 5 seconds
the maximum height is 124 m.
solve for -4.9t^2+49t+1.5=100
or-4.9t^2+49t-98.5=0=4.9t^2-49t+98.5
t=(1/9.8)(49+/-sqrt (2401-1930.6)); square root=21.69
t=70.69/9.8=7.24 sec
t=27.31/9.8=2.79 sec.
those are the times
{{{graph(300,300,-10,10,-50,150,-4.9x^2+49x+1.5,124,100)}}}