Math

Two kids are building a rocket for science class. once the rocket is launched its height in feet, h(t) can be found using the function h(t)=-16t^2+128t where t represents time in seconds. They record the time from the moment the rocket launches until it falls to the ground.

(Is my work for this correct and I also need help with 'F'please)

a) Find the rocket at 3 seconds:
h(t)=-16t^2+128t
h(3)=-16t^2+128t
h=240
b)After how many seconds will the height be 112 feet?
-16t^2+128t=112
-16t+^2+128t-112=0
t=7 and t=0
c)How long after launch does the rocket hit the ground?
-16t+128t=0
-16(t-8)=0
t=8
d)find the maximum height reached by the rocket.
-b/2*a = -128/-16*2= -128/(-32)=4
f) graph height of function with your calculator.
How would I graph this?

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1. (a) correct.
(b) correct
(c) correct
(d) max height is at t=4. But the question was, what is that height? h(4) = 256

No idea how to graph it with your calculator. The graph can be seen at

http://www.wolframalpha.com/input/?i=-16t^2%2B128t

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2. Thank you. but how did you get 256? I tried plugging it back into the original h(4)=-16t+128t but I got 446

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3. 448*

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4. Did you try using

h(t) = -16t^2 + 128t

???

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5. Oh I see what I did yes I got 256 thank you

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