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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 hit the ground?

 Sep 25, 2019
 #1
avatar+106535 
+2

y= -4.9t^2+42t+18.9 

 

The object will hit the ground when y  =  0

 

Use the quadratic formula to find when y = 0

 

-42 ±√ [ 42^2  - 4(-4.9)(18.9) ]                -42 ± √[2134.44]

________________________     =       ______________  =    

                 2(-4.9)                                            -9.8

 

-3/7 sec (reject)   or   9   sec   (accept)

 

 

 

cool cool cool

 Sep 25, 2019
 #2
avatar+139 
+2

This is a Artofproblemsolving alcumas problem....

 Sep 25, 2019
 #3
avatar+2557 
+1

Lol! My math teacher made this    the last question on our algebra quiz last year! Brings back good memories of day dreaming in math class!

CalculatorUser  Sep 26, 2019

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