Results 1 to 7 of 7

Math Help - VERY EASY derivative question

  1. #1
    Junior Member
    Joined
    Apr 2009
    Posts
    28

    Thumbs up VERY EASY derivative question

    Hello,

    I have a very easy question :

    (2+(1/x^2))^{1/2}

    My final answer is -1/x^3(2+1/x^2)^{1/2}

    But the answer sheet gives the answer of -1/2x

    Am I right or wrong ??!

    Thank you
    Last edited by mr fantastic; September 30th 2009 at 11:34 PM. Reason: Fixed latex. Exponents require {} NOT ()
    Follow Math Help Forum on Facebook and Google+

  2. #2
    -1
    e^(i*pi)'s Avatar
    Joined
    Feb 2009
    From
    West Midlands, England
    Posts
    3,053
    Thanks
    1
    Quote Originally Posted by ZaZu View Post
    Hello,

    I have a very easy question :

    (2+(1/x^2))^(1/2)

    My final answer is -1/x^3(2+1/x^2)^(1/2)

    But the answer sheet gives the answer of -1/2x

    Am I right or wrong ??!

    Thank you
    \sqrt{2+x^{-2}} = (2+x^{-2})^{\frac{1}{2}}

    -2x^{-3} \times \frac{1}{2}(2+x^{-2})^{-\frac{1}{2}}

    -\frac{1}{x^3\, \sqrt{2+\frac{1}{x^2}}}
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Junior Member
    Joined
    Apr 2009
    Posts
    28
    Thank you for your reply.

    I got it exactly like yours except that I have a -1 instead of a -2 :S

    There is a step where two 2's cancel, and I get a -1 !

    I just found this out from a buddy through yahoo answers : http://www.wolframalpha.com/input/?i...1%2Fx^2)^1%2F2
    Follow Math Help Forum on Facebook and Google+

  4. #4
    -1
    e^(i*pi)'s Avatar
    Joined
    Feb 2009
    From
    West Midlands, England
    Posts
    3,053
    Thanks
    1
    Quote Originally Posted by ZaZu View Post
    Thank you for your reply.

    I got it exactly like yours except that I have a -1 instead of a -2 :S

    There is a step where two 2's cancel, and I get a -1 !

    I just found this out from a buddy through yahoo answers : http://www.wolframalpha.com/input/?i=derivative+(2%2B1%2Fx^2)^1%2F2
    Yeah, you're right, I forgot to multiply by 0.5 when deriving the square root
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Junior Member
    Joined
    Apr 2009
    Posts
    28
    Hehe thanks for the solving the problem though, you helped me prove that the answer sheet is wrong ^^

    Thanks
    Follow Math Help Forum on Facebook and Google+

  6. #6
    -1
    e^(i*pi)'s Avatar
    Joined
    Feb 2009
    From
    West Midlands, England
    Posts
    3,053
    Thanks
    1
    Quote Originally Posted by ZaZu View Post
    Hehe thanks for the solving the problem though, you helped me prove that the answer sheet is wrong ^^

    Thanks
    You did it not me
    Follow Math Help Forum on Facebook and Google+

  7. #7
    Junior Member
    Joined
    Apr 2009
    Posts
    28
    Thanks for replying
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. [SOLVED] help with easy derivative question half done
    Posted in the Calculus Forum
    Replies: 10
    Last Post: April 1st 2011, 06:46 AM
  2. Basic and easy Derivative question
    Posted in the Calculus Forum
    Replies: 1
    Last Post: October 8th 2010, 02:58 PM
  3. easy derivative question
    Posted in the Calculus Forum
    Replies: 1
    Last Post: November 18th 2009, 07:07 PM
  4. Seemingly easy question... too easy.
    Posted in the Pre-Calculus Forum
    Replies: 3
    Last Post: August 23rd 2009, 09:36 PM
  5. Stupid, Easy Anti-Derivative Question.
    Posted in the Calculus Forum
    Replies: 12
    Last Post: August 29th 2007, 09:49 PM

Search Tags


/mathhelpforum @mathhelpforum