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A problem from polynomials

  1. Apr 24, 2016 #1
    1. The problem statement, all variables and given/known data

    Th value of 'a' for which the equation x3+ax+1=0 and x4+ax+1=0 have a common root is?


    2. Relevant equations


    3. The attempt at a solution

    i initially thought of subtracting both the equations and then finding x and substituting back in the equation but it did not work.
     
  2. jcsd
  3. Apr 24, 2016 #2

    Samy_A

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    Please show how you did it, and why it did not work.
    What you write seems to be the way to go.
     
  4. Apr 24, 2016 #3
    thank you for replying sir
    subtracting we get x4-x3=0
    x can be 1 or 0.
    substituting back in the equation we get a = -2
    but answer given is -1.
     
  5. Apr 24, 2016 #4

    Samy_A

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    a = -2 : looks correct to me.
     
  6. Apr 24, 2016 #5
    than you sir for replying
    then answer must be wrong,sorry for wasting your time
     
  7. Apr 24, 2016 #6

    Samy_A

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    No need to apologize: when a given answer looks wrong (something that can happen), the best you can do is ask to see if others agree.
     
  8. Apr 24, 2016 #7
    yes sir thank you very much
     
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