Results 1 to 4 of 4

Math Help - [SOLVED] Solving for two unknowns

  1. #1
    Solomoreno
    Guest

    [SOLVED] Solving for two unknowns

    For the love of God, will someone please solve the following problem and then kindly explain to me how they did it? If you do so and you live in Springfield, Ohio, I will buy you something under $10. K?

    7x-5y=13
    2x-7y=26
    9x-12y=?
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Moo
    Moo is offline
    A Cute Angle Moo's Avatar
    Joined
    Mar 2008
    From
    P(I'm here)=1/3, P(I'm there)=t+1/3
    Posts
    5,618
    Thanks
    6
    Hello,

    I'll steal your money, better way to get something


    Just add term by term the two equalities.

    (7x-5y)+(2x-7y) = 9x-12y

    But 7x-5y is ... ? And 2x-7y... ?
    Follow Math Help Forum on Facebook and Google+

  3. #3
    GAMMA Mathematics
    colby2152's Avatar
    Joined
    Nov 2007
    From
    Alexandria, VA
    Posts
    1,172
    Awards
    1
    Quote Originally Posted by Solomoreno View Post
    For the love of God, will someone please solve the following problem and then kindly explain to me how they did it? If you do so and you live in Springfield, Ohio, I will buy you something under $10. K?

    7x-5y=13
    2x-7y=26
    9x-12y=?
    Notice that 7x+2x=9x and -5y-7y=-12y. The top two equations add up to equal to the third equation. Therefore ? = 13 + 26 \Rightarrow 39
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Super Member
    earboth's Avatar
    Joined
    Jan 2006
    From
    Germany
    Posts
    5,829
    Thanks
    123
    Quote Originally Posted by Solomoreno View Post
    For the love of God, will someone please solve the following problem and then kindly explain to me how they did it? If you do so and you live in Springfield, Ohio, I will buy you something under $10. K?

    7x-5y=13
    2x-7y=26
    9x-12y=?
    It looks to me as if you have started to solve

    \left|\begin{array}{lcr}7x-5y&=&13\\2x-7y&=&26 \end{array}\right. ... If so multiply the first equation by (-2) and the second one by (+7). That is necessary to get coefficients of x which have the same value but opposite signs:

    \left|\begin{array}{lcr}-14x+10y&=&-26\\14x-49y&=&182 \end{array}\right. ... Now add columnwise(?):

    -39y = 156~\implies~\boxed{y = -4} ... Plug in this value into one of the original equations (it doesn't matter which one) and solve for x.

    I've got x = -1
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Solving for radius in terms of two unknowns
    Posted in the Trigonometry Forum
    Replies: 2
    Last Post: November 15th 2011, 08:05 AM
  2. solving for two unknowns?
    Posted in the Algebra Forum
    Replies: 3
    Last Post: January 13th 2011, 12:57 AM
  3. Solving unknowns
    Posted in the Algebra Forum
    Replies: 2
    Last Post: January 3rd 2010, 02:16 AM
  4. solving for unknowns
    Posted in the Algebra Forum
    Replies: 2
    Last Post: July 7th 2008, 11:48 PM
  5. solving for 3 unknowns
    Posted in the Math Topics Forum
    Replies: 3
    Last Post: July 9th 2007, 10:39 AM

/mathhelpforum @mathhelpforum