SOLUTION: An object is thrown downward with an initial velocity of 7 feet per second. The relationship between the distance s it travels and time t is given by s=7t+16t^2. How long does it t

Question 1161261: An object is thrown downward with an initial velocity of 7 feet per second. The relationship between the distance s it travels and time t is given by s=7t+16t^2. How long does it take the object to fall 78 feet?
Found 2 solutions by math_helper, Boreal:
Answer by math_helper(2461) (Show Source): You can put this solution on YOUR website!

Solutions are:
t = 2
t = -39/16 <<< discard, negative time is N/A
sec
Check: s at t=2: 16(4) + 7(2) = 64 + 14 = 78 (ok)
Answer by Boreal(15235) (Show Source): You can put this solution on YOUR website!
s=7t+16t^2=78
so 16t^2+7t-78=0
(16t+39)(t-2)=0
t=2 seconds.

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