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Quadratic word problems (standard form)

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Problem

Rui is a professional deep water free diver.
His altitude (in meters relative to sea level), x seconds after diving, is modeled by:
d(x)=12x210x
How many seconds after diving will Rui reach his lowest altitude?
  • Your answer should be
  • an integer, like 6
  • a simplified proper fraction, like 3/5
  • a simplified improper fraction, like 7/4
  • a mixed number, like 1 3/4
  • an exact decimal, like 0.75
  • a multiple of pi, like 12 pi or 2/3 pi
seconds
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