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    Blahhh's Avatar
    Blahhh Posts: 1, Reputation: 1
    New Member
     
    #1

    Jan 19, 2009, 01:59 PM
    Math elimination
    how do I solve this in steps
    2x+3y=18
    5x-y=11
    galactus's Avatar
    galactus Posts: 2,271, Reputation: 282
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    #2

    Jan 20, 2009, 10:29 AM
    Solve the bottom equation for y and sub into the top one. Then, the top one will be entirely in terms of x. Solve away.
    ROLCAM's Avatar
    ROLCAM Posts: 1,420, Reputation: 23
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    #3

    Jan 29, 2009, 05:51 PM

    2x+3y=18
    5x-y=11

    Multiply the second equation by 3.
    Eliminate the ys.
    Add up the xs and equivalents
    Then take it from there.
    shatriya's Avatar
    shatriya Posts: 156, Reputation: 18
    Junior Member
     
    #4

    Jan 30, 2009, 07:25 AM
    Quote Originally Posted by Blahhh View Post
    how do i solve this in steps
    2x+3y=18
    5x-y=11
    Basics of solving the equations is that you need to make any element same in both the equations.

    Like,
    2x+3y=18 ------> equation 1
    and 5x-y=11 -----> equation 2
    now you have to see that how can you make one element equal in both the equations.
    either multiply eq 1 by 5 and eq 2 by 2
    then the equation will become,
    10x+15y=90 ------> equation 3
    and 10x-2y=22 -----> equation 4
    So we got 10x as common in both the equations
    But this was a little hectic because we have to do a lot of multiplication, we are humans and we are supposed to make things easier.
    So, multiply equation 2 by 3, that's it
    then the equation will become,
    2x+3y=18 ------> equation 3
    15x-3y=33------> equation 4
    So we got 3y as common.
    Now, add eq 3 to eq 4,
    where +3y will cancel -3y
    we'll get,
    17x=51 => x=51/17 => x=3
    Put the value of x in either eq1 or eq 2 and get value of y

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