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need_help!

Find an ordered pair that is a solution of the system 4 2 1 3 2 3 x y x y + = - - =

  • 2 years ago
  • 2 years ago

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  1. need_help!
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    What the..? Wait.

    • 2 years ago
  2. need_help!
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    4x+2y=-1 3x-2y=3

    • 2 years ago
  3. Hero
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    Add the equations together and what do you get?

    • 2 years ago
  4. need_help!
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    Hmm

    • 2 years ago
  5. need_help!
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    How do I add them?

    • 2 years ago
  6. chris
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    Combine all of the like terms. Since you know that 4x+2y=-1 and 3x-2y=3, you also know that 4x+2y + 3x -2y = -1 + 3

    • 2 years ago
  7. need_help!
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    so, x=2/7 ?

    • 2 years ago
  8. chris
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    good work =)

    • 2 years ago
  9. chris
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    now how do you get y when x=2/7?

    • 2 years ago
  10. need_help!
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    umm, i think you just substitute right? O.o

    • 2 years ago
  11. chris
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    yep =) [just plug x=2/7 back into either equation]

    • 2 years ago
  12. need_help!
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    Yay! This is easy =D Thank youu.

    • 2 years ago
  13. chris
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    No problem. Now the general way to solve these types of problems (systems of equations), is to solve for one variable first, and then substitute back into the other equation. To do this, you mus have a separate equation for each unknown variable - for example in this problem there are two equations and two unknowns.

    • 2 years ago
  14. need_help!
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    Yes I get it! But for example you have like: 4x+4y=-1 3x-2y=3 What do you do here? you can't cancel the 'y' or 'x' out

    • 2 years ago
  15. chris
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    well, you actually can if you know a small trick.

    • 2 years ago
  16. chris
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    if you know that 3x - 2y = 3, you can multiply both sides by the same number and the equation will still be true (equivalent)

    • 2 years ago
  17. chris
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    in this case, I can multiply both sides by 2

    • 2 years ago
  18. chris
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    so 2(3x -2y) = 2*3

    • 2 years ago
  19. chris
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    6x - 4y = 6

    • 2 years ago
  20. chris
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    Now you can cancel out all of the y's by adding the two equations

    • 2 years ago
  21. chris
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    4x + 4y = 4 6x - 4y = 6

    • 2 years ago
  22. need_help!
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    Aooh! *smart* :P :D

    • 2 years ago
  23. need_help!
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    I like it! Thanks a lot for the help.

    • 2 years ago
  24. chris
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    No problem. There are other ways to solve these types of problems, but just ask here when you find a case where it's hard to find a way to cancel out =). good luck!

    • 2 years ago
  25. need_help!
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    btw, the ordered pairs are : (0,-5/14) and (2/7,0) ?

    • 2 years ago
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