Results 1 to 4 of 4

Math Help - Basic Factoring Roots question

  1. #1
    Member
    Joined
    May 2008
    Posts
    143

    Basic Factoring Roots question

    In the following expression

    3\sqrt[3]x(6y-2x)= 3\sqrt[3]x(6y)-3\sqrt[3]x(2x)=<br />
18\sqrt[3]{xy}-6x\sqrt[3]x

    I do not understand how to decide which number ends up under the radical sign.

    For instance in the first term 3\sqrt[3]x(6y)=<br />
18\sqrt[3]{xy}-6x\sqrt[3]x why does the y get distributed under the radical?

    Where as in the second term 3\sqrt[3]x(2x)=6x\sqrt[3]x the x goes outside the radical instead of under like the above part of the expression. The author does not explain this process and its leaving me very confused.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Super Member
    Joined
    May 2009
    Posts
    527
    Quote Originally Posted by allyourbass2212 View Post
    In the following expression

    3\sqrt[3]x(6y-2x)= 3\sqrt[3]x(6y)-3\sqrt[3]x(2x)=<br />
18\sqrt[3]{xy}-6x\sqrt[3]x

    I do not understand how to decide which number ends up under the radical sign.

    For instance in the first term 3\sqrt[3]x(6y)=<br />
18\sqrt[3]{xy}-6x\sqrt[3]x why does the y get distributed under the radical?
    It shouldn't. That's a mistake. The y should remain outside the radical:
    3\sqrt[3]x(6y)=18y\sqrt[3]{x}

    If the y was under the radical to begin with, like this:
    3\sqrt[3]x(6{\color{red}\sqrt[3]{y}}-2x)= 3\sqrt[3]x(6{\color{red}\sqrt[3]{y}})-3\sqrt[3]x(2x)=<br />
18\sqrt[3]{xy}-6x\sqrt[3]x

    then the y should remain under the radical:
    3\sqrt[3]x(6\sqrt[3]{y})=18\sqrt[3]{xy}


    Where as in the second term 3\sqrt[3]x(2x)=6x\sqrt[3]x the x goes outside the radical instead of under like the above part of the expression.
    This is correct.


    01
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Member
    Joined
    May 2008
    Posts
    143
    This books is horrible, full of errors and very brief on explanations.

    At any rate should the variable always go outside the radical in such cases?
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Super Member
    Joined
    May 2009
    Posts
    527
    If you're talking about this case:
    3\sqrt[3]x(6{\color{red}y})=18{\color{red}y}\sqrt[3]{x}

    then the answer is yes.


    01
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. A basic factoring question
    Posted in the Algebra Forum
    Replies: 2
    Last Post: July 24th 2010, 10:10 AM
  2. Another basic factoring question
    Posted in the Algebra Forum
    Replies: 2
    Last Post: July 8th 2009, 01:34 PM
  3. Basic Factoring Question
    Posted in the Algebra Forum
    Replies: 2
    Last Post: July 8th 2009, 10:51 AM
  4. Basic Factoring question
    Posted in the Algebra Forum
    Replies: 3
    Last Post: June 19th 2009, 10:21 AM
  5. Basic Factoring Question
    Posted in the Algebra Forum
    Replies: 5
    Last Post: August 22nd 2008, 09:33 AM

Search Tags


/mathhelpforum @mathhelpforum