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HELP!!!!!!! A falling object travels a distance given by the formula d=3t+5t2, where d is measured in feet and t is measured in second
Question
HELP!!!!!!!
A falling object travels a distance given by the formula d=3t+5t2, where d is measured in feet and t is measured in seconds. How many seconds will it take for the object to travel 84 feet?
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Mathematics
4 years
2021-08-01T04:33:48+00:00
2021-08-01T04:33:48+00:00 1 Answers
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Answers ( )
Answer:
Approximately 3.81 seconds
Step-by-step explanation:
d = 3t + 5t²
d = 84
84 = 3t + 5t²
3t + 5t² – 84 = 0
5t² + 3t – 84 = 0
5(t² + 3/5t – 84/5) = 0
5(((t + 3/10)² – 9/100) – 84/5) = 0
5((t + 3/10)² – 9/100 – 84/5) = 0
5((t + 3/10)² – 9/100 – 1680/100) = 0
5((t + 3/10)² – 1689/100) = 0
5(t + 3/10)² – 1689/20 = 0
5(t + 3/10)² = 1689/20
(t + 3/10)² = 1689/100
t + 3/10 = ±√(1689)/10
t = -3/10 ± √(1689)/10
t = -3/10 ± ≈41.1/10
t = -3/10 ± ≈4.11
t ≈ -0.3 ± 4.11
t [can only be positive] ≈ 4.11 – 0.3
t ≈ 3.81