Posted by **Mary** on Friday, April 13, 2012 at 12:04pm.

Please explain to work this:

A rocket is launched from atop a 105-foot cliff with an initial velocity of 156ft/s. the height of the rocket above the ground at time t is given by

h= -16t^2 + 156t + 105. When will the

rocket hit the ground after it is launched? Round to the nearest second.

- math -
**Steve**, Friday, April 13, 2012 at 12:20pm
naturally, when h = 0.

-16t^2 + 156t + 105 = 0

t = (39 ± √1941)/8

t = 10 sec

- math -
**Nix The Robot**, Friday, April 13, 2012 at 4:40pm
???????????????????????????????????????Your confusing me! STOP CONFUSING ME!!!!!

- math -
**anonymous**, Wednesday, May 18, 2016 at 8:09pm
h=0, so you set this up in the quadratic formula, which then you follow all the rules and your left with a positive and negative answer. time cant be negative, so the correct answer should be about 10.38 seconds which rounds off to 10.4

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