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Math Help - Subsitution and elimination help

  1. #1
    LOL
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    Subsitution and elimination help

    Solve the linear systems using substitution

    y=x+1
    y=2x-4

    y=x+1
    y=2x-4

    Solve the linear systems using elimination

    6x+3y=27
    -6x+2y=-2

    4x+3y=21
    4x-5y=29

    Could someone please explain substitution and elimination for me, thanks for your help.
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  2. #2
    MHF Contributor

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    Quote Originally Posted by LOL View Post
    Solve the linear systems using substitution

    y=x+1
    y=2x-4
    Since y= x+1 in the first equation, substitute x+1 for y in the second equation: y= x+ 1= 2x- 4. Now solve x+ 1= 2x-4 for x and then use y= x+1 to get x.

    y=x+1
    y=2x-4
    ??? This is the same pair of equations!

    Solve the linear systems using elimination

    6x+3y=27
    -6x+2y=-2
    Adding the two equations eliminates x:
    (6x+ 3y)+ (-6x+ 2y)= 27+ (-2)
    (6x- 6x)+ (3y+ 2y)= 27- 2
    5y= 25

    Solve for y and then replace y by that number in either equation to find x.

    4x+3y=21
    4x-5y=29
    Subtract one equation from the other:
    (4x+3y)- (4x-5y)= 21- 29
    (4x- 4x)+ (3y-(-5y)= 21- 29
    8y= -8.

    Could someone please explain substitution and elimination for me, thanks for your help.
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  3. #3
    MHF Contributor
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    Talking

    Quote Originally Posted by LOL View Post
    Could someone please explain substitution and elimination for me, thanks for your help.
    Try some online lessons.
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