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anonymous

  • one year ago

Math help!

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  1. ybarrap
    • one year ago
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    This is concave up |dw:1436133062471:dw| Can guess what it looks like for concave down? That's why f''(x) tells you if an extrema is a max or a min. If f'(x) < 0 then f'(x)=0 is min, if f''(x> > 0 then f'(x)=0 is a max

  2. ybarrap
    • one year ago
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    |dw:1436133272968:dw|

  3. anonymous
    • one year ago
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    So we see that C is false.

  4. ybarrap
    • one year ago
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    You are correct. f''(x) < 0 means concave DOWN |dw:1436133399021:dw| Here is how to remember what sign of f''(x) means: |dw:1436133435469:dw|

  5. ybarrap
    • one year ago
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    *I meant f''(x)

  6. ybarrap
    • one year ago
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    |dw:1436133535569:dw|

  7. ybarrap
    • one year ago
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    Mouth says min or max

  8. anonymous
    • one year ago
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    So would it be D?

  9. ybarrap
    • one year ago
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    |dw:1436133612871:dw|

  10. ybarrap
    • one year ago
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    You know why B is false, right? https://en.wikipedia.org/wiki/Inflection_point#A_necessary_but_not_sufficient_condition

  11. anonymous
    • one year ago
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    Not really

  12. ybarrap
    • one year ago
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    Just because f''(x)=0 doesn't mean that that point is an inflection point. However, if that point is an inflection point then f''(x)=0. I hope this distinction makes sense. This is like saying if A is true then B is true. However, this does not mean the same as if B is true then A is true. Same logic. For A: If a function is defined in a closed interval, then there are real numbers defined at every point in that interval. If you have any set of real numbers, you can always find the maximum and minimum of this set. Do you agree?

  13. anonymous
    • one year ago
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    Yes I do

  14. ybarrap
    • one year ago
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    Good!

  15. ybarrap
    • one year ago
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    "A" does NOT mean that the Global min and max are in this interval it just means that there IS a max and min in that interval.

  16. anonymous
    • one year ago
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    So its wrong?

  17. ybarrap
    • one year ago
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    No, it's right. Just want to make the distinction between a Global and Local (absolute) min and max.

  18. anonymous
    • one year ago
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    Okay thank you so much! You're very helpful!

  19. ybarrap
    • one year ago
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    You're welcome!

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