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EmmaH

  • 3 years ago

is -x-4x=3x??

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  1. JoãoVitorMC
    • 3 years ago
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    only if x=0

  2. mathstudent55
    • 3 years ago
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    -x is the same as -1x -4x is -4 x If you had -1 -4 what do you get?

  3. mathstudent55
    • 3 years ago
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    -1 - 4 = ?

  4. EmmaH
    • 3 years ago
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    -5?

  5. EmmaH
    • 3 years ago
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    im having a lot of trouble with this Solve the system. y = 2 - x and y = 4x + 7 (1, 1) (1, 3) (-1, 3) (-1, 1) no solution im prettyy sure tis no solution

  6. mathstudent55
    • 3 years ago
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    Right, so since -1 - 4 = -5, then -x - 4x = -5x

  7. mathstudent55
    • 3 years ago
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    Now the system. Again, you have the two equations solved for y already, so use substitution.

  8. mathstudent55
    • 3 years ago
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    Do you remember from the two previous systems what to do next?

  9. EmmaH
    • 3 years ago
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    yes im working ion it

  10. mathstudent55
    • 3 years ago
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    Ok, let me see what you're up to since you're having trouble with it.

  11. EmmaH
    • 3 years ago
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    ok so i had 2-x=4x+7 2-x +2=4x+7+2 -x=4x+9 -x-4x=9 now im stuck

  12. mathstudent55
    • 3 years ago
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    The 2 on the left side is positive, so you need to subtract 2 from both sides.

  13. seanwalsh1984
    • 3 years ago
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    -x (so -1x) take away 4 more x's. It's like being $1 in the hole in the bank account. Spend four more bucks, and you are $5 in the whole, not $3. However... -x - 4x = 3x is interesting because: -x - 4x + x = 3x + x Then we have -4x = 3x Then as said above, if x = 0, then it is true, otherwise no. Hope this helps.

  14. mathstudent55
    • 3 years ago
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    2 - x = 4x + 7 2 - 2 - x = 4x + 7 - 2 -x = 4x + 5 Now subtract 4x from both sides

  15. EmmaH
    • 3 years ago
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    -4-4x=5

  16. mathstudent55
    • 3 years ago
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    -x - 4x = 4x - 4x + 5 -5x = 5

  17. EmmaH
    • 3 years ago
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    x=-1?

  18. mathstudent55
    • 3 years ago
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    |dw:1356283149364:dw|

  19. mathstudent55
    • 3 years ago
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    right, x = -1

  20. mathstudent55
    • 3 years ago
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    Now insert this value of x in one of the original equations, and solve for y

  21. EmmaH
    • 3 years ago
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    sorry i had to do something i do it one sec

  22. EmmaH
    • 3 years ago
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    1,3 ?

  23. mathstudent55
    • 3 years ago
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    y = 3. You're right, but remember x = -1, not x = 1

  24. EmmaH
    • 3 years ago
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    thanks you!

  25. mathstudent55
    • 3 years ago
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    |dw:1356283635553:dw|

  26. mathstudent55
    • 3 years ago
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    You're welcome.

  27. EmmaH
    • 3 years ago
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    one more question The ordered pair (-1, -1) is a solution of the system -4x + 2y = 2 and x + y = -2. True False

  28. EmmaH
    • 3 years ago
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    i think its true

  29. mathstudent55
    • 3 years ago
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    Substitute the ordered pair into both equations. If it makes them both true, it's a solution.

  30. EmmaH
    • 3 years ago
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    ok i did it its true

  31. mathstudent55
    • 3 years ago
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    -4x + 2y = 2 Try (-1, -1) Is -4(-1) + 2(-1) = 2 ? 4 - 2 = 2? Yes. The ordered pair works in the first equation. Now try the second. x + y = -2 Is -1 + (-1 ) = -1 true? -2 = -2. It's true. You are correct, (-1, -1) is a solution.

  32. mathstudent55
    • 3 years ago
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    Good job!

  33. EmmaH
    • 3 years ago
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    =D

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