Results 1 to 4 of 4

Math Help - exponents

  1. #1
    Newbie
    Joined
    Mar 2013
    From
    USA
    Posts
    22

    exponents

    I have the problem in the book of simplify:

    (-a3b3)-2/3

    I get :

    ______1_______
    (-a3b3)2/3


    = _______1______
    (-a2b2)


    The books answer is the same except that a2b2 is positive. Where did I go wrong?

    Thanks
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor

    Joined
    Aug 2006
    Posts
    18,969
    Thanks
    1788
    Awards
    1

    Re: exponents

    Quote Originally Posted by baldysm View Post
    I have the problem in the book of simplify:

    (-a3b3)-2/3

    I get :

    ______1_______
    (-a3b3)2/3


    = _______1______
    (-a2b2)


    The books answer is the same except that a2b2 is positive. Where did I go wrong?

    {\left( { - {a^3}{b^3}} \right)^{\frac{2}{3}}} = {a^2}{b^2}

    i.e. (-a)^2=a^2
    Follow Math Help Forum on Facebook and Google+

  3. #3
    MHF Contributor

    Joined
    Apr 2005
    Posts
    16,454
    Thanks
    1868

    Re: exponents

    Quote Originally Posted by baldysm View Post
    I have the problem in the book of simplify:

    (-a3b3)-2/3

    I get :

    ______1_______
    (-a3b3)2/3


    = _______1______
    (-a2b2)
    You didn't square the "-". This should be \frac{1}{(-a)^2b^2} and, of course, (-a)^2= a^2

    The books answer is the same except that a2b2 is positive. Where did I go wrong?

    Thanks
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Junior Member
    Joined
    Apr 2013
    From
    Canada
    Posts
    42
    Thanks
    2

    Re: exponents

    Plato and HallsofIvy have the right idea. Obviously (-a) 2 = a2, but if it doesn't make sense that (-a 3b3)2/3 = a2b2, think of (-a3*b3) as (-1*a 3 *b3).
    (-1) 2/3 = (-1)2 = 1, or (-1)2/3 = (1)1/3 = 1
    Last edited by HowDoIMath; April 6th 2013 at 08:58 PM.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Exponents for exponents
    Posted in the Algebra Forum
    Replies: 4
    Last Post: September 24th 2012, 12:03 PM
  2. Zero and 1st Exponents
    Posted in the Pre-Calculus Forum
    Replies: 13
    Last Post: September 12th 2008, 10:04 AM
  3. Exponents
    Posted in the Algebra Forum
    Replies: 6
    Last Post: September 7th 2008, 06:15 PM
  4. Need help with exponents
    Posted in the Math Topics Forum
    Replies: 4
    Last Post: August 30th 2008, 06:07 AM
  5. Exponents
    Posted in the Algebra Forum
    Replies: 2
    Last Post: August 18th 2008, 10:51 PM

Search Tags


/mathhelpforum @mathhelpforum