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A problem from polynomials

  • #1

Homework Statement


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


Homework Equations




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.
 

Answers and Replies

  • #2
Samy_A
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Homework Helper
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Homework Statement


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


Homework Equations




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.
Please show how you did it, and why it did not work.
What you write seems to be the way to go.
 
  • #3
Please show how you did it, and why it did not work.
What you write seems to be the way to go.
Please show how you did it, and why it did not work.
What you write seems to be the way to go.
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.
 
  • #4
Samy_A
Science Advisor
Homework Helper
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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.
a = -2 : looks correct to me.
 
  • #5
a = -2 : looks correct to me.
than you sir for replying
then answer must be wrong,sorry for wasting your time
 
  • #6
Samy_A
Science Advisor
Homework Helper
1,241
510
than you sir for replying
then answer must be wrong,sorry for wasting your time
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.
 
  • #7
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.
yes sir thank you very much
 

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