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WynWynn

  • 4 years ago

Solve the system of equations by the addition method. Choose one answer. a. (-2, 1) b. (-2, -1) c. (2, 1) d. (2, -1)

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  1. WynWynn
    • 4 years ago
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  2. gandalfwiz
    • 4 years ago
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    THe addition method is adding one term to another to get a variable to cancel out.

  3. gandalfwiz
    • 4 years ago
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    You can multiply the equations by various numbers first to get the variables just right so they cancel

  4. gandalfwiz
    • 4 years ago
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    It doesn't matter what variable we choose to cancel out. Let's do x

  5. WynWynn
    • 4 years ago
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    ok!

  6. gandalfwiz
    • 4 years ago
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    We need the number in front of the first x to be the opposite of the second x, like 5, -5, or -3, 3, so they'll add to zero.

  7. gandalfwiz
    • 4 years ago
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    Lets multiply the first equation by 5 and the second one by -3 so we'll get a 15x and a -15x

  8. gandalfwiz
    • 4 years ago
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    5(-3x+7y=-1) -15x+35y=-5

  9. gandalfwiz
    • 4 years ago
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    second equation: -3(-5x-4y=14) 15x+12y=-42

  10. gandalfwiz
    • 4 years ago
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    Do you see what I did there?

  11. gandalfwiz
    • 4 years ago
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    wynwyn? uthere?

  12. WynWynn
    • 4 years ago
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    Yes yes yes i see!!

  13. gandalfwiz
    • 4 years ago
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    kk... now u just add the equations together. -15x+35y=-5 + 15x=12y=-42

  14. gandalfwiz
    • 4 years ago
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    (4 second equation: supposed to be 15x+12y=-42)

  15. gandalfwiz
    • 4 years ago
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    so. -15x+15x=0. 35y+12y=47y -5+-42=-47 0+47y=-47

  16. gandalfwiz
    • 4 years ago
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    Now just solve for y. 47y=-47 y=-1

  17. gandalfwiz
    • 4 years ago
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    Now that u know what y is, plug it back into an equation (it doesn't matter which) and solve for x

  18. gandalfwiz
    • 4 years ago
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    -3x+7y=-1 -3x+7(-1)=-1 -3x-7=-1 -3x=6 x=-2

  19. WynWynn
    • 4 years ago
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    ok

  20. gandalfwiz
    • 4 years ago
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    It looks like you want your final answer to be an ordered pair, like a point on a graph. a point is always in the form (x,y), so your final answer is -2,-1

  21. gandalfwiz
    • 4 years ago
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    choice b

  22. WynWynn
    • 4 years ago
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    Thank you so much!!!

  23. gandalfwiz
    • 4 years ago
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    welcome! Medal?

  24. gandalfwiz
    • 4 years ago
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    tnx :)

  25. WynWynn
    • 4 years ago
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    no problem! =D

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