Can someone tell me why the answer to this is 4?

Question

anonymous · Answer

If h(t) represents the height of an object above ground level at time t and h(t) is given by: h(t)=-16t^2+14t+1

find the height of the object when at the time when the speed is zero. 
h(t)=

anonymous · Answer

I posted this question before but never got a clear explanation

anonymous · Answer

speed is zero when it has gone up as far as it can and starts coming back down. that will be at the vertex of this parabola. find the vertex via 
$$-\frac{b}{2a}$$ and that will give you the time.  replace t by that number and you will get the max height

anonymous · Answer

here 
$$a=-16, b = 14,-\frac{b}{2a}=-\frac{14}{2\times -16}=\frac{7}{16}$$

anonymous · Answer

then find 
$$h(\frac{7}{16})$$a nd i guess (although i did not do it) you will get 4. if not then the answer is whatever you get

anonymous · Answer

OK THANKS!!!!!!!

anonymous · Answer

yw