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Simultaneous Equations by Substitution

  • 12-10-2014 7:31pm
    #1
    pruthive
    Registered Users, Registered Users 2 Posts: 7 ✭


    hey all,
    can someone help me to solve these equations by substitution method,

    2x-3y-2=0 , 2x-3y-2 = 0

    every time i did, i end up in a totally unbalanced numbers in both sides, and its not supposed to be. so anyone could help, it'll be great!

    Cheers!
    Tagged:


Comments

  • #2
    biko
    Registered Users, Registered Users 2 Posts: 81,220 ✭✭✭✭biko


    From Blogs forum...


  • #3
    Delphi91
    Registered Users, Registered Users 2 Posts: 1,501 ✭✭✭Delphi91


    You have a mistake there somewhere - both equations are the same!


  • #4
    pruthive
    Registered Users, Registered Users 2 Posts: 7 ✭pruthive


    2x − 3y − 2 = 0, 3x + 8y − 3 = 0

    sorry these are the two equations


  • #5
    dlouth15
    Registered Users, Registered Users 2 Posts: 1,169 ✭✭✭dlouth15


    I would start with the first equation. Express it in the form y=... Then substitute the expression represented by ... into the second equation for y. You then have an equation in one variable, x. Simplify this and you get the answer for x. Then substitute this value for x into the first equation and simplify to get the answer for y.

    Show your attempt so far then we can attempt to identify the mistake and point out the remedy.


  • #6
    Yakuza
    Registered Users, Registered Users 2 Posts: 5,141 ✭✭✭Yakuza


    Express x in terms of y:
    Taking the first expression, you can rearrange it to read : 2x = 3y +2. Divide by 2 to get x=1.5y +1.

    Now, substitute that into the second:
    3x + 8y - 3 = 0 becomes
    3(1.5y + 1) +8y - 3 = 0.
    Expand this to get : 4.5y +3 + 8y -3 = 0
    Gather the terms:
    12.5y=0, so y=0.
    If y = 0, then x is.....? (Left for the OP)


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