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mathcalculus

  • 2 years ago

HELP! how to solve system of equations x-2y+z=-1 y+2z=-4 x+y+3z=-5 what do we do when there is a missing variable??? :(

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  1. woody84
    • 2 years ago
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    what are you solving for??

  2. mathcalculus
    • 2 years ago
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    x,y, and z

  3. mathcalculus
    • 2 years ago
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    I'm not sure what to do since the x is missing.

  4. Directrix
    • 2 years ago
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    Write the system as: x - 2y +z =-1 0x +y+ 2z=-4 x + y + 3z = -5 In the first and third equations, eliminate the variable x. Then, you will have a system of 2 by 2 equations in the unknowns y and z. Of those two equations, eliminate a variable and solve for the other. If you are allowed to use technology, take a look at the online 3 x 3 linear equation system solver at: http://math.bd.psu.edu/~jpp4/finitemath/3x3solver.html @mathcalculus

  5. Directrix
    • 2 years ago
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    Question?

  6. mathcalculus
    • 2 years ago
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    thank you

  7. mathcalculus
    • 2 years ago
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    im trying to solve it step by step

  8. Directrix
    • 2 years ago
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    x - 2y +z =-1 0x +y+ 2z=-4 x + y + 3z = -5 x - 2y +z =-1 x - 2y +z =-1 x + y + 3z = -5 --multiply through by -1 -> -x - y - 3z = 5 ---------------- -3y - 2z = 4

  9. mathcalculus
    • 2 years ago
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    ok

  10. mathcalculus
    • 2 years ago
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    i got a little lost. now i know why

  11. mathcalculus
    • 2 years ago
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    i got that, so what about the second equation?

  12. Directrix
    • 2 years ago
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    @mathcalculus Your Task: Solve this system - Just add them. -3y - 2z = 4 y+ 2z=-4 -----------------

  13. mathcalculus
    • 2 years ago
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    it bothers me that the 0x is there.

  14. Directrix
    • 2 years ago
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    Don't look at it. When I eliminated the "x" in equations #1 and #3, the 0x was not an issue.

  15. mathcalculus
    • 2 years ago
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    i got this: -2y=0

  16. mathcalculus
    • 2 years ago
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    but it can't be. it's undefined.

  17. Directrix
    • 2 years ago
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    Note that here: Solve this system - Just add them. -3y - 2z = 4 y+ 2z=-4 ----------------- I excluded the 0x term. It is just a placeholder of sorts.

  18. mathcalculus
    • 2 years ago
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    0/2?

  19. mathcalculus
    • 2 years ago
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    yeah i know.

  20. Directrix
    • 2 years ago
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    -2y = 0 y= 0/2 y = 0--> You have division by 0 and division into 0 mixed up.

  21. mathcalculus
    • 2 years ago
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    so y is 0?

  22. mathcalculus
    • 2 years ago
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    okay i got that step right.

  23. mathcalculus
    • 2 years ago
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    z=2

  24. mathcalculus
    • 2 years ago
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    x=-6

  25. mathcalculus
    • 2 years ago
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    it's wrong... :(

  26. Directrix
    • 2 years ago
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    It is wrong. But, unless you show your steps, I cannot help you find the error.

  27. mathcalculus
    • 2 years ago
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    z=-2

  28. mathcalculus
    • 2 years ago
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    ok hold on.

  29. mathcalculus
    • 2 years ago
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    i got it right! x=1 y=0 z=-2 ! =]

  30. mathcalculus
    • 2 years ago
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    thanks so much! i really aprreciate it!

  31. Directrix
    • 2 years ago
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    You are welcome.

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