Question 869917
{{{ graph( 300, 200, -25, 25, -300, 300, -16x^2+128x+20 ) }}}
This is a parabola with time (t) along the x axis and height (h) along the y axis.  From the graph, the rocket looks like it achieves max height of 260 feet after 4 seconds.
Also, you can use calculus and take the first derivative and set it equal to 0 to determine the time t for the max height.
f' = -32t + 128
-32t + 128 = 0
32t = 128
t = 4
now we can determine the max height by subsituting for t in oringal equation
h = -16*4^2 +128*4 + 20 = 266 feet
the vertex of the parabola is (4, 266)