SOLUTION: A model rocket is launched with an initial upward velocity of 65 m/s The rocket's height h (in meters) after t seconds is given by the following. h= 65t -5t^2. Find all values of t

Algebra ->  Quadratic Equations and Parabolas -> SOLUTION: A model rocket is launched with an initial upward velocity of 65 m/s The rocket's height h (in meters) after t seconds is given by the following. h= 65t -5t^2. Find all values of t      Log On


   

Question 1150599: A model rocket is launched with an initial upward velocity of 65 m/s The rocket's height h (in meters) after t seconds is given by the following. h= 65t -5t^2. Find all values of t for which the rocket's height is 30 meters.Round your answer(s) to the nearest hundredth.
Answer by ikleyn(52756) About Me  (Show Source):
You can put this solution on YOUR website!
.

    h(t) = 30 meters,   or


    -5t^2 + 65t = 30

     5t^2 - 65t + 30 = 0

      t^2 - 13t + 6  = 0

      t%5B1%2C2%5D = %2813+%2B-+sqrt%2813%5E2+-+4%2A6%29%29%2F2 = %2813+%2B-+sqrt%28145%29%29%2F2.


There are two roots  t%5B1%5D = %2813+-+sqrt%28145%29%29%2F2 = 0.479 seconds (approximately, ascending),   and

                     t%5B2%5D = %2813+%2B+sqrt%28145%29%29%2F2 = 12.521 seconds (approximately, descending).      ANSWER

Solved.