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Basic solving for variable question.

  1. Aug 5, 2011 #1
    1. The problem statement, all variables and given/known data
    if (4x+1) + 6 = 9, then x=?


    2. Relevant equations



    3. The attempt at a solution

    the answer is -1 and 1/2, but how could -1 work wouldn't that make the answer 3 instead of 9.
     
  2. jcsd
  3. Aug 5, 2011 #2

    Mark44

    Staff: Mentor

    The equation is linear, so there can be only one solution (x = 1/2). Are you sure you have written the equation correctly?
     
  4. Aug 5, 2011 #3
    I meant to say 1/2 or -1 but I feel like they screwed up its a sample placement test with my university.
     
  5. Aug 5, 2011 #4

    Mark44

    Staff: Mentor

    The only solution to the equation you gave is x = 1/2.
     
  6. Aug 5, 2011 #5
    okay thanks I've never had a question answered so fast in a forum before, I was trying out this forum compared to another one but this forum wins hands down lol.
     
  7. Aug 5, 2011 #6

    eumyang

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    Homework Helper

    I still think there's a possibility that you didn't copy the question right. If there were absolute value symbols instead of parentheses:
    |4x+1| + 6 = 9
    ... then there would indeed be two solutions, -1 and 1/2.
     
  8. Aug 5, 2011 #7

    Mark44

    Staff: Mentor

    I'll bet that's it. My thought was that there might be an exponent missing, but that didn't work out.
     
  9. Aug 6, 2011 #8

    HallsofIvy

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    Staff Emeritus
    Science Advisor

    The other possibility is that some fool, who typed up the exam, replaced "|" with "(" and ")"!
     
  10. Aug 6, 2011 #9
    answer is only 1/2,and i dont know how you got -1.
     
  11. Aug 6, 2011 #10

    HallsofIvy

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    Staff Emeritus
    Science Advisor

    Did you not read the other replies? The problem is, almost certainly, to solve
    |4x+ 1|+ 6= 9, not (4x+ 1)+ 6= 9.
     
  12. Aug 6, 2011 #11

    Ray Vickson

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    Either that, or the questioner wrote "and" instead of "or" in a multiple-choice setting (or the OP copied the question incorrectly).

    RGV
     
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