Quantcast

Got Homework?

Connect with other students for help. It's a free community.

  • across
    MIT Grad Student
    Online now
  • laura*
    Helped 1,000 students
    Online now
  • Hero
    College Math Guru
    Online now

Here's the question you clicked on:

55 members online
  • 0 replying
  • 0 viewing

mathcalculus

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??? :(

  • 8 months ago
  • 8 months ago

  • This Question is Closed
  1. woody84
    Best Response
    You've already chosen the best response.
    Medals 0

    what are you solving for??

    • 8 months ago
  2. mathcalculus
    Best Response
    You've already chosen the best response.
    Medals 0

    x,y, and z

    • 8 months ago
  3. mathcalculus
    Best Response
    You've already chosen the best response.
    Medals 0

    I'm not sure what to do since the x is missing.

    • 8 months ago
  4. Directrix
    Best Response
    You've already chosen the best response.
    Medals 1

    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

    • 8 months ago
  5. Directrix
    Best Response
    You've already chosen the best response.
    Medals 1

    Question?

    • 8 months ago
  6. mathcalculus
    Best Response
    You've already chosen the best response.
    Medals 0

    thank you

    • 8 months ago
  7. mathcalculus
    Best Response
    You've already chosen the best response.
    Medals 0

    im trying to solve it step by step

    • 8 months ago
  8. Directrix
    Best Response
    You've already chosen the best response.
    Medals 1

    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

    • 8 months ago
  9. mathcalculus
    Best Response
    You've already chosen the best response.
    Medals 0

    ok

    • 8 months ago
  10. mathcalculus
    Best Response
    You've already chosen the best response.
    Medals 0

    i got a little lost. now i know why

    • 8 months ago
  11. mathcalculus
    Best Response
    You've already chosen the best response.
    Medals 0

    i got that, so what about the second equation?

    • 8 months ago
  12. Directrix
    Best Response
    You've already chosen the best response.
    Medals 1

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

    • 8 months ago
  13. mathcalculus
    Best Response
    You've already chosen the best response.
    Medals 0

    it bothers me that the 0x is there.

    • 8 months ago
  14. Directrix
    Best Response
    You've already chosen the best response.
    Medals 1

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

    • 8 months ago
  15. mathcalculus
    Best Response
    You've already chosen the best response.
    Medals 0

    i got this: -2y=0

    • 8 months ago
  16. mathcalculus
    Best Response
    You've already chosen the best response.
    Medals 0

    but it can't be. it's undefined.

    • 8 months ago
  17. Directrix
    Best Response
    You've already chosen the best response.
    Medals 1

    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.

    • 8 months ago
  18. mathcalculus
    Best Response
    You've already chosen the best response.
    Medals 0

    0/2?

    • 8 months ago
  19. mathcalculus
    Best Response
    You've already chosen the best response.
    Medals 0

    yeah i know.

    • 8 months ago
  20. Directrix
    Best Response
    You've already chosen the best response.
    Medals 1

    -2y = 0 y= 0/2 y = 0--> You have division by 0 and division into 0 mixed up.

    • 8 months ago
  21. mathcalculus
    Best Response
    You've already chosen the best response.
    Medals 0

    so y is 0?

    • 8 months ago
  22. mathcalculus
    Best Response
    You've already chosen the best response.
    Medals 0

    okay i got that step right.

    • 8 months ago
  23. mathcalculus
    Best Response
    You've already chosen the best response.
    Medals 0

    z=2

    • 8 months ago
  24. mathcalculus
    Best Response
    You've already chosen the best response.
    Medals 0

    x=-6

    • 8 months ago
  25. mathcalculus
    Best Response
    You've already chosen the best response.
    Medals 0

    it's wrong... :(

    • 8 months ago
  26. Directrix
    Best Response
    You've already chosen the best response.
    Medals 1

    It is wrong. But, unless you show your steps, I cannot help you find the error.

    • 8 months ago
  27. mathcalculus
    Best Response
    You've already chosen the best response.
    Medals 0

    z=-2

    • 8 months ago
  28. mathcalculus
    Best Response
    You've already chosen the best response.
    Medals 0

    ok hold on.

    • 8 months ago
  29. mathcalculus
    Best Response
    You've already chosen the best response.
    Medals 0

    i got it right! x=1 y=0 z=-2 ! =]

    • 8 months ago
  30. mathcalculus
    Best Response
    You've already chosen the best response.
    Medals 0

    thanks so much! i really aprreciate it!

    • 8 months ago
  31. Directrix
    Best Response
    You've already chosen the best response.
    Medals 1

    You are welcome.

    • 8 months ago
    • Attachments:

See more questions >>>

Your question is ready. Sign up for free to start getting answers.

spraguer (Moderator)
5 → View Detailed Profile

is replying to Can someone tell me what button the professor is hitting...

23

  • Teamwork 19 Teammate
  • Problem Solving 19 Hero
  • You have blocked this person.
  • ✔ You're a fan Checking fan status...

Thanks for being so helpful in mathematics. If you are getting quality help, make sure you spread the word about OpenStudy.

This is the testimonial you wrote.
You haven't written a testimonial for Owlfred.