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ValentinaT

  • 3 years ago

Using substitution, could someone please help me with this system? –y + 3x = 6 y = –6x + 12 So far I've gotten: Substituting the second equation into the first you get -(-6x+12) + 3x = 6 Which can be solved for x after finding x you can use the second equation above directly to find y

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  1. MathDad72
    • 3 years ago
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    Sounds like you know what you are doing .... What's the problem you are having?

  2. ValentinaT
    • 3 years ago
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    Well, I had help with that part, but I can't figure out what to do next. I tried using my textbook, but it was a bit confusing, because they showed you what to do, but didn't explain it.

  3. MathDad72
    • 3 years ago
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    Ok, first let's distribute that -(-6x+12) Can you do that?

  4. ValentinaT
    • 3 years ago
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    -6x + -72?

  5. MathDad72
    • 3 years ago
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    Think of it this way: (-)(-6x) & (-)(12)

  6. ValentinaT
    • 3 years ago
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    Because negative times negative equals a positive 6x + -12?

  7. MathDad72
    • 3 years ago
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    yes, very good so we have 6x-12+3x=6 What will you do next?

  8. ValentinaT
    • 3 years ago
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    Add 6x and 3x?

  9. MathDad72
    • 3 years ago
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    correct 9x-12=6 now what?

  10. ValentinaT
    • 3 years ago
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    Substitute for y from the other equation?

  11. MathDad72
    • 3 years ago
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    Let's try to solve for x.

  12. ValentinaT
    • 3 years ago
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    Sorry, I was looking at my textbook, and thought that we were onto that step.

  13. MathDad72
    • 3 years ago
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    :-) That's ok.

  14. ValentinaT
    • 3 years ago
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    Okay, so how would I go about solving for x? Also, thank you for the medal.

  15. MathDad72
    • 3 years ago
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    We have x on one side, can we get non x-values on the other side?

  16. ValentinaT
    • 3 years ago
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    You would add 12 + 6? Then get 18, divided by 9x would equal 2.

  17. MathDad72
    • 3 years ago
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    Excellent: So x=2

  18. ValentinaT
    • 3 years ago
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    Okay.

  19. MathDad72
    • 3 years ago
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    What are you going to do with that x=2?

  20. MathDad72
    • 3 years ago
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    You still there?

  21. ValentinaT
    • 3 years ago
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    Substitute 2 for x in either equation and solve for y? Sorry, my computer is slow sometimes.

  22. MathDad72
    • 3 years ago
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    Heh I Understand. You are correct, good job!

  23. ValentinaT
    • 3 years ago
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    Thank you! So, -y + 3(2) + 6.

  24. MathDad72
    • 3 years ago
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    -y+3(2)=6

  25. ValentinaT
    • 3 years ago
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    So, -y + 6 = 6.

  26. MathDad72
    • 3 years ago
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    correct

  27. ValentinaT
    • 3 years ago
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    What would I do next?

  28. MathDad72
    • 3 years ago
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    same that you did when you had 9x-12=6 and solved for x. now we are going to it for y

  29. ValentinaT
    • 3 years ago
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    6 - 6 = 0 So y, would be 0?

  30. MathDad72
    • 3 years ago
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    That is correct.

  31. ValentinaT
    • 3 years ago
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    Then I would substitute 0for y, and get 0 + 6 = 6.

  32. MathDad72
    • 3 years ago
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    Correct: So your Answer is: X=2, y=0

  33. MathDad72
    • 3 years ago
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    As long as you get a correct statement when you plug them both back in, like you showed 6=6 and not get something like 7=6, then we would have a problem.

  34. ValentinaT
    • 3 years ago
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    Okay, thank you some much for your help. If I could give you more than one medal I would.

  35. MathDad72
    • 3 years ago
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    Thank you, It is nice to meet someone who wants to work out the problems and not just demand an answer.

  36. ValentinaT
    • 3 years ago
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    I get what you mean, you are a very good teacher by the way.

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