Results 1 to 6 of 6

Math Help - Need help solving this Simultaneous Equation

  1. #1
    Newbie
    Joined
    Dec 2008
    Posts
    4

    Need help solving this Simultaneous Equation

    Okay I have these

    A+B = 5
    4A+ -2/3B = -8

    I have a rough idea of what the answer is and my answers are no where near it; this is what I have

    Times A+B = 5 by 2
    Times 4A + -2/3B = -8 by 3

    2A + 2B = 10
    12A + -2B = -24

    14A = -14
    A = -14/14 = -1

    is this correct so far?
    Last edited by oligo; February 24th 2011 at 04:52 AM.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Super Member
    Joined
    Jan 2008
    Posts
    588
    Thanks
    87
    Yes, now substitute A = -1 into one of the equations to get B
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Dec 2008
    Posts
    4
    okay do you get -6

    I get this;

    12A+-2B = -24
    12(-1) + 24 = 2B

    12=2B

    12/-2 = B

    b= -6
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Super Member Quacky's Avatar
    Joined
    Nov 2009
    From
    Windsor, South-East England
    Posts
    901
    Quote Originally Posted by oligo View Post
    2A + 2B = 10
    12A + -2B = -24
    This is a small typo - you have obtained the correct result for A.

    Edit:

    A + B = 5.

    If A = -1

    -1 + B = 5

    Does B = -6?
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Newbie
    Joined
    Dec 2008
    Posts
    4
    okay think I have it now, answer is +6 correct?

    I made the mistake by putting a minus on the 2 here; 12/-2 = B (should be 12/2 = B)
    Follow Math Help Forum on Facebook and Google+

  6. #6
    Super Member Quacky's Avatar
    Joined
    Nov 2009
    From
    Windsor, South-East England
    Posts
    901
    Quote Originally Posted by oligo View Post
    okay think I have it now, answer is +6 correct?

    I made the mistake by putting a minus on the 2 here; 12/-2 = B (should be 12/2 = B)
    That's right. Remember that you can (and perhaps, if unsure, should) check by substituting into both equations to make sure you get the same result.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. solving simultaneous equations
    Posted in the Pre-Calculus Forum
    Replies: 3
    Last Post: September 3rd 2011, 03:55 AM
  2. Replies: 2
    Last Post: April 10th 2010, 05:30 AM
  3. simultaneous equation problem solving
    Posted in the Algebra Forum
    Replies: 4
    Last Post: February 11th 2010, 02:42 AM
  4. Solving simultaneous equations
    Posted in the Algebra Forum
    Replies: 2
    Last Post: August 25th 2009, 06:03 AM
  5. Simultaneous equations, Graphing, Equation Solving
    Posted in the Pre-Calculus Forum
    Replies: 1
    Last Post: October 25th 2008, 02:34 PM

Search Tags


/mathhelpforum @mathhelpforum