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The equation y = -4.9t^2 + 42t + 18.9 describes the height (in meters) of a ball tossed up in the air at 42 meters per second from a height of 18.9 meters from the ground, as a function of time in seconds. In how many seconds will the ball reach a height of 12 feet?.

 Apr 12, 2022
 #1
avatar+122390 
+1

12 ft  =  12 (.3048)  = 3.6576 m

 

3.6576  =  -4.9t^2 + 42t + 18.9

 

-4.9t^2 + 42t + 15.2424  = 0

 

Using the quadratic formula, the ball reaches 12 ft  at

 

-42 -  sqrt ( 42^2 - 4 (-4.9)(15.2424) )                -42  - sqrt (2062.75104)

__________________________  =              ___________________   ≈   8.92 sec

                 2 * -4.9                                                          -9.8

 

 

cool cool cool

 Apr 12, 2022
 #2
avatar+122 
-2

Mhm but i need help

 Apr 12, 2022

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