Advanced Alegebra

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How do I solve the following problems?

My homework was to correct a puiz that I failed, but I do not know how to solve these problems..please help!

Solving systems of equations using elimination:

7.) 10x - 10y = 0
5x - 4y = 8
Answer (8,8)
I got the right answer because this one was multiple choice, but it was because I guessed...I need to know how to work it out.

8.) -8x - 8y = -8
-5x + 16y = 16

9.)I need this one worked out...I guessed the right answer (7, -7)

2x + 3yy = -7
-3x - 2y = -7

10.) -8x + 8y = -16
-3x + 7y = 10

11. 8x + 14y = 128
6x + 2y = 62

  • Advanced Alegebra -

    if 10x-10y=0, then 10x=10y, or x=y
    plug that into the other equation to get
    5x-4x = 8
    x=8, so y=8

    the others are basically the same. you can substitute, or eliminate.

    -8x - 8y = -8
    -5x + 16y = 16

    x+y=1, so y = 1-x
    -5x + 16(1-x) = 16
    -21x = 0
    x=0, so y=1

    -8x + 8y = -16
    -3x + 7y = 10

    multiply top by 3 and bottom by -8 to get

    -24x + 24y = -48
    24x - 56y = -80

    add them up to get
    -32y = -128
    y = 4, so x = 6

    Try the others and come back if you get stuck. Show us whatcha got, and we can straighten it out if necessary.

    If you get an answer, be sure to plug the values back into both original equations to make sure it is right.

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