Optimization

AP Calculus AB· difficulty 3/5

A closed box with square base has surface area 9696. Maximum volume?

  • A

    6464

    check_circle
  • B

    3232

  • C

    4848

  • D

    9696

Explanation

S=2s2+4sh=96h=(962s2)/(4s)=(48s2)/(2s)S = 2s^2 + 4 s h = 96 \Rightarrow h = (96 - 2s^2)/(4s) = (48 - s^2)/(2s). V=s2h=s(48s2)/2V = s^2 h = s(48 - s^2)/2. V=(483s2)/2=0s2=16,s=4V' = (48 - 3s^2)/2 = 0 \Rightarrow s^2 = 16, s = 4. Then h=32/8=4h = 32/8 = 4 and V=64V = 64.

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