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jesusisabiscuit Group Title

The derivative of f(x)=(x^4/3)-(x^5/5) attains its maximum value at what x value? a. -1 b. 0 c. 1 d. 4/3 e. 5/3

  • one year ago
  • one year ago

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  1. Lilmoney Group Title
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    B

    • one year ago
  2. jesusisabiscuit Group Title
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    can you explain it to me, please?

    • one year ago
  3. Lilmoney Group Title
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    Hold on

    • one year ago
  4. Yahoo! Group Title
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    find f''(x)

    • one year ago
  5. jesusisabiscuit Group Title
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    f''(x) = 4x^2 - 3x^3 what next?

    • one year ago
  6. Lilmoney Group Title
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    Isn't that it

    • one year ago
  7. wio Group Title
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    Ummm, looks like your \(f''(x)\) is a bit off.

    • one year ago
  8. Yahoo! Group Title
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    The condition To attain Max is f''(x) > 0

    • one year ago
  9. Lilmoney Group Title
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    That is true

    • one year ago
  10. wio Group Title
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    They want the max of the derivative.

    • one year ago
  11. wio Group Title
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    So you want to find the critical numbers \(f''(x)=0\) or undefined. Then you'd plug them back into \(f'(x)\) to see where the max is.

    • one year ago
  12. Yahoo! Group Title
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    nope @wio they ask..For where the max is attained

    • one year ago
  13. wio Group Title
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    "The derivative of f(x)=(x^4/3)-(x^5/5) attains its maximum" "f'(x) attains its maximum"

    • one year ago
  14. jesusisabiscuit Group Title
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    aha! f"(x) = 4x^2 - 4x^3. i got my critical numbers. x = 0 & x = 1?

    • one year ago
  15. KingGeorge Group Title
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    That looks good. So your local maximum value is at either x=0 or x=1. Also, since your first derivative is a negative quartic (has a \(-x^4\) term), you have a parabola type shape opening downwards, so the local maximum is the global maximum. Now you just need to determine which one is the maximum.

    • one year ago
  16. KingGeorge Group Title
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    make sense so far?

    • one year ago
  17. jesusisabiscuit Group Title
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    i think. i got f'(0) = 0 and f'(1) = 1/3. so the answer is... 1?

    • one year ago
  18. KingGeorge Group Title
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    Bingo.

    • one year ago
  19. jesusisabiscuit Group Title
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    All riiiiiiiiight. thank you. and wio. but s/he left.

    • one year ago
  20. KingGeorge Group Title
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    You're welcome.

    • one year ago
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