Results 1 to 3 of 3

Math Help - Indices

  1. #1
    Newbie
    Joined
    Nov 2008
    Posts
    2

    Indices

    1. if 2160 = 2^a*3^b*5^c , find values of a, b and c
    2. Show that \frac{y^-1}{x^-1+y^-1} + \frac{y^-1}{x^-1-y^-1} = \frac{2xy}{y^2-x^2}

    my attempt on the second one:
    LHS \frac{x+y}{y}+\frac{x-y}{y} ===> <br />
\frac{x+y+x-y}{y} = \frac {2x}{y} <br />
    Should the RHS in question be \frac{2x}{y} ? :S
    Last edited by Anish; January 8th 2009 at 05:37 AM.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    Joined
    Sep 2008
    From
    West Malaysia
    Posts
    1,261

    Re :

    Quote Originally Posted by Anish View Post
    2. Show that \frac{y^-1}{x^-1+y^-1} + \frac{y^-1}{x^-1-y^-1} = \frac{2xy}{y^2-x^2}

    my attempt on the second one:
    LHS \frac{x+y}{y}+\frac{x-y}{y} ===> <br />
\frac{x+y+x-y}{y} = \frac {2x}{y} <br />
    Should the RHS in question be \frac{2x}{y} ? :S
    \frac{1/y}{1/x+1/y}+\frac{1/y}{1/x-1/y}

    =\frac{xy}{y^2+yx}+\frac{xy}{y^2-yx}

    =\frac{xy^3-x^2y^2+xy^3+x^2y^2}{y^4-x^2y^2}

    Take out the common factor y^2 , you should get the RHS .

    * Note that the equation above is valid ..
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Nov 2008
    Posts
    2
    oops , how silly of me !
    Thanks a lot mathaddict.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Indices
    Posted in the Algebra Forum
    Replies: 2
    Last Post: November 9th 2009, 01:18 AM
  2. indices
    Posted in the Algebra Forum
    Replies: 6
    Last Post: November 8th 2009, 07:01 AM
  3. Indices
    Posted in the Algebra Forum
    Replies: 2
    Last Post: November 7th 2009, 04:52 AM
  4. indices
    Posted in the Algebra Forum
    Replies: 1
    Last Post: January 28th 2009, 05:26 AM
  5. INDICES
    Posted in the Algebra Forum
    Replies: 6
    Last Post: October 28th 2008, 12:34 PM

Search Tags


/mathhelpforum @mathhelpforum