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need_help! Group Title

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! Group Title
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    What the..? Wait.

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

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

    • 2 years ago
  4. need_help! Group Title
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    Hmm

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

    • 2 years ago
  6. chris Group Title
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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! Group Title
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    so, x=2/7 ?

    • 2 years ago
  8. chris Group Title
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    good work =)

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

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

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

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

    • 2 years ago
  13. chris Group Title
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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! Group Title
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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 Group Title
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    well, you actually can if you know a small trick.

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

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

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

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

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

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

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

    • 2 years ago
  24. chris Group Title
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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! Group Title
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    btw, the ordered pairs are : (0,-5/14) and (2/7,0) ?

    • 2 years ago
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