Are the Sum of Polynomial Roots Always Zero When Complex Numbers Are Involved?

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Discussion Overview

The discussion revolves around the properties of polynomial roots, particularly focusing on whether the sum of the roots is always zero when complex numbers are involved. Participants explore the implications of Vieta's formulas and the application of polynomial rules in the context of complex roots.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant notes that for the polynomial equation x^5=1, the sum of the roots is zero, questioning if this is due to Vieta's formula where -b/a equals zero when b is zero.
  • Another participant references Vieta's formulas as a general case for understanding polynomial roots.
  • A different participant asserts that the sum of the roots of x^n=1 is zero because the roots can be visualized as vertices of a regular n-gon.
  • One participant reiterates the application of Vieta's formula, emphasizing that the sum of the roots is the negative of the coefficient of x^{n-1} for monic polynomials, regardless of the field.
  • Another participant expresses confusion about the application of polynomial rules to complex numbers and seeks clarification on whether these rules hold true in the complex field.
  • One participant mentions that their teacher indicated that the rules do not apply, leading to their doubt about the topic.

Areas of Agreement / Disagreement

Participants express differing views on the applicability of polynomial rules to complex numbers, with some asserting that the rules hold true while others question this assertion based on personal instruction. The discussion remains unresolved regarding the application of these rules in the context of complex roots.

Contextual Notes

There are indications of confusion regarding the definitions of coefficients in polynomial equations and how they relate to the sum of roots, particularly in the context of complex numbers. Some participants express uncertainty about the implications of their examples and the general applicability of polynomial rules.

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u noe how x^5=1 has 5 roots which some of them are not real in complex field.

and so is x^2=-64 with roots = -8i or 8i



and i notice that the sum of roots = 0 (msut inculde non real --> complex number)

is this becasue of the rule of polynomial --> -b/a = sum of roots


for this case b always =0 so -b/a = 0 ?


or (there is nothing to do with this and my example are just a fulke) once complex number is incolved then polynoimial rules can not apply?
 
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so this is current
 
what do you mean current? this result is well known, and I would suggest has been for very long time. The sum of all roots of x^n=1, n>1 (and be extension other numbers) is zero since, for example, they form the vertices of a regular n-gon.
 
great i mean is this because of [tex]\frac{-b}{a}[/tex]

sum of roots of a equation ax^n+bx^(n-1)+cx^(n-2)...


this case x^2+0x^1 + 64=0 , x^2=-64


sum of roots 0/a = 0
 
Last edited:
What's b what's a? The 'rules' about polynomials apply irrespective of the field, whereby I think you mean that for a monic polynomial of degree n the sum of the roots is the negative of the coeff of x^{n-1}

your explanation appears retrospectively...
 
~~_~~~ sorry i m bad at explaning

for example an equation of

[tex]a_{n}x^{n}+a_{n-1}x^{n-1}+...+a_{1}x+a_{0}[/tex]

which a_{n} = a a_{n-1} = b

so simmilar it can be write as
[tex]ax^n+bx^{n-1}+...[/tex]

this case

x^2= -64

a= 1 b= 0


anyway wat i mean is that can rules of polynomial be applied to complex numbers



omg i always confusing ppl how can i improve my explaning? help!
 
Last edited:
Why wouldn't the 'rules' of polynomials apply when the field is C?
 
thx thanks all cause my teacher said no and i doubt
 

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