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Finding the Directional derivative

  1. Jul 17, 2006 #1
    Find the directional derivative of f (x, y) = 5−x2−2y2 at P (-1, -1).
    anybody pls help as i don't know how to find the direction from this ques so , i can't find the directional derivative

    pls help
  2. jcsd
  3. Jul 17, 2006 #2
    Your question seems to be incomplete; please provide the complete question as it is given in the book. The directional derivative is the rate at which a function changes at some point in a particular direction.
  4. Jul 17, 2006 #3


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    I think that's what he's trying to figure out.

    If you have absolutely no clue what direction it's in, I would guess that it's in the direction of the vector from the origin to P. Not for any particular reason, but because it's a better guess than anything else :confused:
  5. Jul 17, 2006 #4


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  6. Jul 17, 2006 #5


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    One more time: the problem as stated makes no sense. teng125, please state the entire problem as given in your textbook.
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