Results 1 to 5 of 5

Math Help - Radical Equations

  1. #1
    MHF Contributor
    Joined
    Jul 2008
    From
    NYC
    Posts
    1,489

    Radical Equations

    I found the following question in my Math B book.
    It is a radical equation problem. I played with this question for 20 minutes and got nowhere.

    Here it is:

    8x^(-3/4) = 27

    Solve for x.

    The answer is x = 16/81. How do I get this answer?
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Junior Member
    Joined
    Mar 2009
    Posts
    66
    Quote Originally Posted by magentarita View Post
    I found the following question in my Math B book.
    It is a radical equation problem. I played with this question for 20 minutes and got nowhere.

    Here it is:

    8x^(-3/4) = 27

    Solve for x.

    The answer is x = 16/81. How do I get this answer?
    8x^\frac{-3}{4}=27
    x^\frac{-3}{4}=\frac{27}{8}
    -0.75logx=log\frac{27}{8}
    logx=(log\frac{27}{8})/-0.75=D D is just for simplicity in the last line.
    10^D=\frac{16}{81}
    Follow Math Help Forum on Facebook and Google+

  3. #3
    MHF Contributor
    Joined
    Jul 2008
    From
    NYC
    Posts
    1,489

    logs???

    Quote Originally Posted by JeWiSh View Post
    8x^\frac{-3}{4}=27
    x^\frac{-3}{4}=\frac{27}{8}
    -0.75logx=log\frac{27}{8}
    logx=(log\frac{27}{8})/-0.75=D D is just for simplicity in the last line.
    10^D=\frac{16}{81}
    I know about applying logs but this question is located in the radical equations chapter. How do you find x using radical equations?
    Follow Math Help Forum on Facebook and Google+

  4. #4
    MHF Contributor
    Joined
    Sep 2008
    From
    West Malaysia
    Posts
    1,261
    Quote Originally Posted by magentarita View Post
    I found the following question in my Math B book.
    It is a radical equation problem. I played with this question for 20 minutes and got nowhere.

    Here it is:

    8x^(-3/4) = 27

    Solve for x.

    The answer is x = 16/81. How do I get this answer?

    8x^{-\frac{3}{4}}=27

    x^{-\frac{3}{4}}=\frac{27}{8}

     <br />
x=(\frac{27}{8})^{-\frac{4}{3}}<br />
    Follow Math Help Forum on Facebook and Google+

  5. #5
    o_O
    o_O is offline
    Primero Espada
    o_O's Avatar
    Joined
    Mar 2008
    From
    Canada
    Posts
    1,407
    Just to elaborate, we're making use of the fact that:

    \left(\displaystyle x^{ \displaystyle \frac{a}{b}}\right)^{ \displaystyle \frac{b}{a}} = \displaystyle x

    So for your question, mathaddict raised both sides to the power of -\tfrac{4}{3} .
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Solving Radical equations
    Posted in the Algebra Forum
    Replies: 1
    Last Post: March 14th 2010, 06:22 PM
  2. Radical Equations
    Posted in the Algebra Forum
    Replies: 3
    Last Post: April 10th 2009, 04:59 AM
  3. Radical Equations
    Posted in the Algebra Forum
    Replies: 2
    Last Post: March 8th 2009, 06:53 PM
  4. radical equations
    Posted in the Algebra Forum
    Replies: 4
    Last Post: July 2nd 2008, 05:12 PM
  5. Help on Radical Equations
    Posted in the Algebra Forum
    Replies: 5
    Last Post: January 28th 2007, 04:53 AM

Search Tags


/mathhelpforum @mathhelpforum