Arock is thrown and follows the curve given by the equation d = -t2 + 4t + 5, where d is the distance in feet and t is the time in seconds. when will the rock hit the ground? 9 seconds 5 seconds 2 seconds 1 second

5 seconds

Step-by-step explanation:

The relationship between "d" and "the ground" is not described. If we assume that "d" is distance above the ground, then the rock will hit the ground when d=0. This gives rise to the quadratic equation ...

-t^2 +4t +5 = 0

-(t -5)(t +1) = 0

t = 5 or t = -1 are solutions. Only the positive solution is useful.

The rock will hit the ground after 5 seconds.

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step-by-step explanation:

54 km / hours

step-by-step explanation:

we need to convert seconds to hours

60 seconds = 1 minutes

60 minutes = 1hour

15 m         60 second   60 minutes

  * *         = 54000 meters/ hour

second     1 minute             1 hour

now we need to convert meters to km

1000 m = 1 km

54000 m       1 km

*   = 54 km / hours

hour               1000m