Question 188705
Suppose you throw a ball upward with a starting velocity of 30ft/s. The ball is 6ft high when it leaves your hand. After how many seconds will it hit the ground? 
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Equation that gives the height of the object after t seconds.
s(t) = -16t^2 + 30t + 6
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The height will be zero when the object hits the ground.
-16t^2 + 30t + 6 = 0
-8t^2 + 15t + 3 = 0
Use the quadratic formula to get:
t = [-15 +- sqrt(225 - 4*-8*3)]/(-16)
t = [-15 - 17.92]/(-16)
t = 2.07 seconds
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Cheers,
Stan H.