Directional derivative

  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. 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. Office_Shredder

    Office_Shredder 4,487
    Staff Emeritus
    Science Advisor
    Gold Member

    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. Astronuc

    Staff: Mentor

  6. HallsofIvy

    HallsofIvy 41,269
    Staff Emeritus
    Science Advisor

    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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