Roots of a squared polynomial ( complex numbers)

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Homework Statement



problem in a pic attached

Homework Equations





The Attempt at a Solution


i solved i and ii a , when it came to b , i just said that every one of the 3 roots will be squared having 2 roots 1 + and 1 - but then i read the marking schemes ( also attached) , and i got really confused and now i dont know what he wants from me
 

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Answers and Replies

  • #2
Ray Vickson
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Homework Statement



problem in a pic attached

Homework Equations





The Attempt at a Solution


i solved i and ii a , when it came to b , i just said that every one of the 3 roots will be squared having 2 roots 1 + and 1 - but then i read the marking schemes ( also attached) , and i got really confused and now i dont know what he wants from me

He wants you to tell him what are all the square roots of -2, -2+2*sqrt(3)*i and -2 - 2*sqrt(3)*i.
 
  • #3
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He wants you to tell him what are all the square roots of -2, -2+2*sqrt(3)*i and -2 - 2*sqrt(3)*i.

why cant i just say (z+2)^2= 0 and solve and do the same for the complex roots?
why do i have to find the roots of the -2?
 
  • #4
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why cant i just say (z+2)^2= 0 and solve and do the same for the complex roots?
why do i have to find the roots of the -2?

(z + 2)2 is not a factor of p(z2). It is a factor of (p(z))2, however, a completely different polynomial.
The polynomial is not the object being squared. p(z2) only means that the variable z is being replaced with the variable z2. So, as a result, we know that z2 + 2 is a factor.
 
  • #5
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(z + 2)2 is not a factor of p(z2). It is a factor of (p(z))2, however, a completely different polynomial.
The polynomial is not the object being squared. p(z2) only means that the variable z is being replaced with the variable z2. So, as a result, we know that z2 + 2 is a factor.
okay...thanks very much, tht was a tricky one, or maybe i am stupid :D
either way , thanks , i got it
 

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