Results 1 to 5 of 5

Math Help - Strategies for Solving Linear Equations (are step 1 and 2 mixed up?)

  1. #1
    Newbie
    Joined
    Oct 2010
    Posts
    10

    Strategies for Solving Linear Equations (are step 1 and 2 mixed up?)

    According to my book, and some sources I've found on the internet, the common strategy for solving a linear equation is:
    1) If fractions are present, multiply each side by the LCD to eliminate them. If decimals are present, multiply each side by a power of 10 to eliminate them.
    2) Use the distributive property to remove parentheses.
    3) Combine any like terms.
    4) Use the addition property of equality to get all variables on one side and numbers on the other.
    5) Use the multiplication property of equality to get a single variable on one side.
    6) Check by replacing the variable in the original equation with your solution.

    My problem is 1) and 2). I've learned the hard way that if you multiply each side by the LCD before distributing to any fractions within parentheses, you get the wrong answer.

    Attached is my wrong answer with work shown. To come up with the right answer, at step 1 I needed to distribute the 1/2 and 1/3 to the parenthesis first.
    Is there any reason to not do step 2 in the strategy as a general rule before step 1? Why would they be in that order if it sometimes does not work?

    Thank you,
    Chris

    Strategies for Solving Linear Equations (are step 1 and 2 mixed up?)-problem81.jpg
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor Unknown008's Avatar
    Joined
    May 2010
    From
    Mauritius
    Posts
    1,260
    Your problem is when distributing the LCD.

    6(2 + 4(y+2) \neq 12 + 8(6y + 12)

    6(2 + 4(y+2) = 12 + 8(y + 2)

    It's like

    6(3x) = 18x

    You don't put (18)(6x) = 72x
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Oct 2010
    Posts
    10
    So don't distribute the LCD (or factor of 10 in the case of decimals) to inside the parentheses. But would it make a difference if I just started removing all parentheses as step 1 prior to dealing with fractions/decimals with LCD/factor of 10?
    Follow Math Help Forum on Facebook and Google+

  4. #4
    MHF Contributor Unknown008's Avatar
    Joined
    May 2010
    From
    Mauritius
    Posts
    1,260
    If you removed all the parenthesis before distributing the LCD, then you multiply each term, yes.
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Newbie
    Joined
    Oct 2010
    Posts
    10
    Thank you!
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 6
    Last Post: November 30th 2011, 02:41 AM
  2. Advanced Problem-Solving Strategies
    Posted in the Advanced Applied Math Forum
    Replies: 0
    Last Post: June 14th 2011, 05:42 AM
  3. Advanced Problem-Solving Strategies
    Posted in the Advanced Math Topics Forum
    Replies: 0
    Last Post: June 14th 2011, 05:42 AM
  4. Solving Linear equations
    Posted in the Algebra Forum
    Replies: 1
    Last Post: April 4th 2008, 08:16 PM
  5. Mixed Strategies Help
    Posted in the Discrete Math Forum
    Replies: 0
    Last Post: December 27th 2007, 06:54 AM

Search Tags


/mathhelpforum @mathhelpforum