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Fraction Differentiation

  1. Jan 31, 2015 #1
    1. The problem statement, all variables and given/known data
    Differentiate the following functions with respect to x

    2. Relevant equations
    (√2x-1)/ (lnx)?

    3. The attempt at a solution

    ln x (2x-10)^-1/2 -√(2x-1)(1/x)/(ln x)^2
    ........................................................{This is a denominator}
    thank you

     
  2. jcsd
  3. Jan 31, 2015 #2

    HallsofIvy

    User Avatar
    Staff Emeritus
    Science Advisor

    The only error I see is an obvious typo- that "2x- 10" should be "2x- 1".
     
  4. Jan 31, 2015 #3
    So it is right ?

    there is no any factor right ?!
    and this is the last answer isn't it ?

    Thank you :)
     
  5. Jan 31, 2015 #4

    Mark44

    Staff: Mentor

    The function (it's not an equation) you are differentiating is ambiguous. You wrote √2x-1 as the numerator. Which one of these did you mean?
    1. ##\sqrt{2}x - 1##
    2. ##\sqrt{2x} - 1##
    3. ##\sqrt{2x - 1}##
    From your answer, it seems that what you intended was #3 above. If you use the √ for square roots, use parentheses to indicate what's inside the radical, like so: √(2x - 1).
     
  6. Jan 31, 2015 #5
    Sorry for that

    I was meaning the third one :)

    TQ
     
  7. Jan 31, 2015 #6

    Mark44

    Staff: Mentor

    Since this is a calculus problem, I am moving it to the Calculus section.
     
  8. Jan 31, 2015 #7
    Thank You

    so what is your opinion about this answer ?
    I have an exam tomorrow :(
     
  9. Jan 31, 2015 #8

    Mark44

    Staff: Mentor

    As already mentioned, 2x - 10 should be 2x - 1.

    Also, as you wrote the above, it would be incorrect. You need parentheses or brackets around the entire numerator -- [ln x (2x-1)^(-1/2) -√(2x-1)(1/x)]/(ln x)^2 -- and you should have parentheses around the -1/2 exponent.

    Regarding the numerator, if you write a + b/2, this is seen by almost everyone as a + (b/2). To make your intentions clear, write this as (a + b)/2. That was my point in the previous paragraph.
     
  10. Jan 31, 2015 #9
    Thank you so much
    but can you show me how can I write like this form above
    TQ
     
  11. Jan 31, 2015 #10

    Mark44

    Staff: Mentor

    Do you mean using LaTeX?
    If so, here's what I wrote in post #4,
    1. # #\sqrt{2}x - 1# #
    2. # #\sqrt{2x} - 1# #
    3. # #\sqrt{2x - 1}# #
    Each pair of # # characters should be written WITHOUT the extra space. With the extra space, you can see the LaTeX script without it being rendered in the browser.

    The # # pairs are used for inline LaTeX. For standalone LaTeX, use $ $ (again, without the spaces). You can also use [ itex] and [ /itex], or [ tex] and [ /tex] tags at the beginning and end of your expressions. I prefer to use # # pairs or sometimes $ $ pairs, since they require less typing.
    For a brief tutorial on LaTeX, see https://www.physicsforums.com/help/latexhelp/.
     
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