SOLUTION: please help me A ball is thrown from an initial height of 5 feet with an initial upward velocity of 21 ft/s. The ball's height h (in feet) after t seconds is given by the follo

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Question 1173200: please help me
A ball is thrown from an initial height of 5 feet with an initial upward velocity of 21 ft/s. The ball's height h (in feet) after t seconds is given by the following.
+h=5%2B21t-16t%5E2+
Find all values of t for which the ball's height is 11 feet.
Round your answer(s) to the nearest hundredth.
Found 2 solutions by ewatrrr, ikleyn:
Answer by ewatrrr(24785) About Me  (Show Source):
You can put this solution on YOUR website!


Hi  



A ball is thrown from an initial height of 5 feet with an initial upward velocity of 21 ft/s. 

The ball's height h (in feet) after t seconds is given by the following.

+h=5%2B21t-16t%5E2+

Find all values of t for which the ball's height is 11 feet.

11 = 5+21t-16t^2

16t^2 -21t + 6 = 0                 t+=+%2821+%2B-+sqrt%28+57+%29%29%2F%2832%29+

t = .89sec  and t = .42sec       

Wish You the Best in your Studies.

Answer by ikleyn(52802) About Me  (Show Source):
You can put this solution on YOUR website!
.

To find these values of "t", solve the equation


    5 + 21t - 16t^2 = 11   feet.


Reduce it to the standard form


    16t^2 - 21t + 6 = 0.


Use the quadratic formula.