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The equation y = -6t^2 + 51t describes the height (in feet) of a projectile launched from the surface of Mars at 51 feet per second. In how many seconds will the projectile first reach 108 feet in height?

 May 30, 2019
 #1
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We need to solve this

 

108  = - 6t^2 + 51t      rearrange as

 

6t^2 - 51t + 108  = 0       divide through by 3

 

2t^2 - 17t + 36  = 0        factor

 

(2t  - 9) (t - 4)  = 0

 

Set each factor to 0 and solve

 

2t -9 = 0                                         t - 4  =0

2t = 9                                             t = 4 sec

t = 9/2 sec = 4.5 sec

 

So...4 sec

 

cool cool cool

 May 30, 2019

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