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The equation y=-16t^2 + 60t describes the height (in feet) of a projectile launched from the ground at 60 feet per second upward. In how many seconds will the projectile first reach 56 feet in height? Express your answer as a decimal rounded to the nearest hundredth.

 Jun 11, 2019
 #1
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We need to solve this

 

-16t^2 + 60t = 56     rearrange as

 

16t^2 - 60t + 56 = 0       divide through by 4

 

4t^2 - 15t + 14  = 0   factor

 

(4t - 7) (t - 2)  = 0

 

Set each factor to 0 and solve for t  and we get   7/4 sec  and 2 sec

 

7/4 sec is correct  = 1.75 sec

 

 

cool cool cool

 
 Jun 11, 2019
edited by CPhill  Jun 11, 2019

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