Results 1 to 3 of 3

Math Help - Equation with 2 sets of Brackets

  1. #1
    Newbie
    Joined
    Jan 2011
    Posts
    21

    Equation with 2 sets of Brackets

    I can do these normally but this one has confused me.

    4(3x-7)-5(2x-4)

     <br />
12x-28-10x+20=3x<br />
    Then I get

     <br />
2x-8=3x<br />
    so

    x = -8/5

    This is wrong, why?
    x is supposed to = -8
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    Prove It's Avatar
    Joined
    Aug 2008
    Posts
    11,653
    Thanks
    1478
    I assume that the starting equation is actually \displaystyle 4(3x-7) - 5(2x-4) = 3x.

    You are correct up to \displaystyle 2x - 8 = 3x

    \displaystyle 2x - 8 - 2x = 3x - 2x

    \displaystyle -8 = x.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Jan 2011
    Posts
    21
    That's right. but where's the extra 2x come from?


    OOOMG I see, why do I make things SOOOOO much harder than they actually are??!! For some reason I was adding 2x to one side and subtracting it from the other.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. graph equation with weird | brackets
    Posted in the Algebra Forum
    Replies: 2
    Last Post: May 31st 2011, 12:09 PM
  2. Brackets
    Posted in the Calculus Forum
    Replies: 4
    Last Post: November 21st 2010, 12:00 PM
  3. Brackets
    Posted in the Math Topics Forum
    Replies: 1
    Last Post: January 26th 2010, 12:21 PM
  4. brackets
    Posted in the Math Topics Forum
    Replies: 1
    Last Post: January 26th 2010, 12:19 PM
  5. brackets
    Posted in the Math Topics Forum
    Replies: 5
    Last Post: October 22nd 2009, 07:55 AM

Search Tags


/mathhelpforum @mathhelpforum