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lovelycharm

  • one year ago

elimination 4x - 7y = 3 x - 7y = -15

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  1. mjr632
    • one year ago
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    Do you understand how to substitute?

  2. lovelycharm
    • one year ago
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    yeh

  3. mjr632
    • one year ago
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    Okay, firstly, you want one equation as either Y or X by itself.

  4. mjr632
    • one year ago
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    If you do that part, i'll then explain the next step.

  5. lovelycharm
    • one year ago
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    okay wat the next step

  6. mjr632
    • one year ago
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    write the equation you've got for your isolated variable in here.

  7. lovelycharm
    • one year ago
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    |dw:1360887641308:dw| is that right how i solve for y

  8. Rachel98
    • one year ago
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    - 7y + - 7y is not zero and 4x + x is 5x

  9. Rachel98
    • one year ago
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    You need a variable to cross out when you add down. Try multiplying one of the equations by a certain number so that one variable crosses out when you add down.

  10. lovelycharm
    • one year ago
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    could u show me the step please @Rachel98

  11. Rachel98
    • one year ago
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    Okay, here is an example problem I'll draw it.

  12. Rachel98
    • one year ago
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    |dw:1360888023089:dw|

  13. Rachel98
    • one year ago
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    Now see how none of the variables cross off? So I'm going to try multiplying the first equation by - 1 and see what happens.

  14. Rachel98
    • one year ago
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    |dw:1360888146491:dw|

  15. Rachel98
    • one year ago
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    Now see if you add straight down a variable crosses off when you add down. - y and y can also be put as - 1y and 1y. Look at the numbers - 1 + 1 = 0, so that crosses off.

  16. Rachel98
    • one year ago
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    |dw:1360888346035:dw|

  17. Rachel98
    • one year ago
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    Now all we have to do is divide both sides by - 1, so undo the multiplication

  18. Rachel98
    • one year ago
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    |dw:1360888489391:dw|

  19. Rachel98
    • one year ago
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    So we have our x value, now what about y? What we do is we plug in the x value (substitute 8 for x) in one of the original equations. In this case the bottom equation is easier to do this.

  20. lovelycharm
    • one year ago
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    could u help me with my problem cuz i dont understand ur problem

  21. Rachel98
    • one year ago
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    |dw:1360888601809:dw|

  22. Rachel98
    • one year ago
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    See, in my problem how I multiplied one equation by - 1? Try doing that with either one of your equations and then add down.

  23. Rachel98
    • one year ago
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    Remember, a negative * a negative is a positive.

  24. Rachel98
    • one year ago
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    |dw:1360888933281:dw|

  25. Rachel98
    • one year ago
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    Did you get it? Give it a try. I'll check your answer and if you make a mistake I'll work through it for you.

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