Results 1 to 5 of 5

Math Help - Negative fraction with exponent?

  1. #1
    Newbie
    Joined
    Jan 2011
    Posts
    2

    Negative fraction with exponent?

    The negative sign is confusing. Granted it's like *-1, but with the exponent, i don't know how it should look. I have a test coming up, and these are a couple of practice ones that I got. Please let me know if I'm on the right track.

    1)

    -4^5
    ------
    -4^2 =-4^3 = (-4) (-4) (-4) = -64 ???

    2)

    ( 2 )^3
    - (-----)
    ( 3 )

    = (-1) (-2) (-2) (-2) = 8
    -----
    = (-1) (-3) (-3) (-3) = 27 ???

    Thanks
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Master Of Puppets
    pickslides's Avatar
    Joined
    Sep 2008
    From
    Melbourne
    Posts
    5,236
    Thanks
    29
    Hi there Mesoc,

    Quote Originally Posted by Mesoc View Post
    1)

    -4^5
    ------
    -4^2 =-4^3 = (-4) (-4) (-4) = -64 ???

    Which one is your equation?


    \displaystyle\frac{-4^5}{-4^2} = -4^{5-2} = -4^3 = -(4\times 4\times 4) = -64


    \displaystyle \frac{(-4)^5}{(-4)^2} = (-4)^{5-2} = (-4)^3 = -4\times -4\times -4 = -64


    You won't always get the same answer!



    Quote Originally Posted by Mesoc View Post


    2)

    ( 2 )^3
    - (-----)
    ( 3 )

    = (-1) (-2) (-2) (-2) = 8
    -----
    = (-1) (-3) (-3) (-3) = 27 ???
    Just guessing again,

    \displaystyle -\left(\frac{2}{3} \right)^3 = -\left(\frac{2^3}{3^3} \right) = \frac{-8}{27}
    Follow Math Help Forum on Facebook and Google+

  3. #3
    -1
    e^(i*pi)'s Avatar
    Joined
    Feb 2009
    From
    West Midlands, England
    Posts
    3,053
    Thanks
    1
    The minus sign is largely the same as multiplying by -1. So -a = -1 \cdot a

    When you have an exponent you can do that and then use the law (ab)^c = a^cb^c although it only works if the minus sign is part of the base being raised. If it's outside the brackets then you act upon it after the exponent

    For example (-2)^2 = (-1 \cdot -2)^2 = (-1)^2 \cdot (-2)^2 = +4 whereas -(2^2) = -1 \cdot 4 = -4

    You should always use brackets to make it clear which case you mean
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Newbie
    Joined
    Jan 2011
    Posts
    2
    [QUOTE=pickslides;610788]Hi there Mesoc,



    Which one is your equation?


    \displaystyle\frac{-4^5}{-4^2} = -4^{5-2} = -4^3 = -(4\times 4\times 4) = -64


    You won't always get the same answer!

    ^ that's the equation. They love throwing these negatives in to screw with us.




    Just guessing again,

    \displaystyle -\left(\frac{2}{3} \right)^3 = -\left(\frac{2^3}{3^3} \right) = \frac{-8}{27}[/QUOTE

    That's correct, but stupid question...why is there a negative in front of the 8, instead of the fraction? or does it not matter?


    ----

    Thanks ei, that cleared up a rule i was unsure of.
    Follow Math Help Forum on Facebook and Google+

  5. #5
    MHF Contributor
    Joined
    Mar 2010
    From
    Florida
    Posts
    3,093
    Thanks
    5
    [QUOTE=Mesoc;610922]
    Quote Originally Posted by pickslides View Post
    Hi there Mesoc,



    Which one is your equation?


    \displaystyle\frac{-4^5}{-4^2} = -4^{5-2} = -4^3 = -(4\times 4\times 4) = -64


    You won't always get the same answer!

    ^ that's the equation. They love throwing these negatives in to screw with us.




    Just guessing again,

    \displaystyle -\left(\frac{2}{3} \right)^3 = -\left(\frac{2^3}{3^3} \right) = \frac{-8}{27}[/QUOTE

    That's correct, but stupid question...why is there a negative in front of the 8, instead of the fraction? or does it not matter?


    ----

    Thanks ei, that cleared up a rule i was unsure of.
    Doesn't matter.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 1
    Last Post: November 13th 2011, 06:30 PM
  2. Replies: 3
    Last Post: April 27th 2011, 05:53 PM
  3. negative exponent
    Posted in the Pre-Calculus Forum
    Replies: 1
    Last Post: April 16th 2009, 09:23 PM
  4. Negative Exponent
    Posted in the Algebra Forum
    Replies: 5
    Last Post: January 2nd 2009, 08:44 AM
  5. Replies: 1
    Last Post: August 19th 2008, 09:41 AM

Search Tags


/mathhelpforum @mathhelpforum