If a + b + c = 0, then show that

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Homework Help Overview

The problem involves proving the equation 6(a^5 + b^5 + c^5) = 5(a^3 + b^3 + c^3)(a^2 + b^2 + c^2) under the condition that a + b + c = 0. The subject area pertains to algebraic identities and polynomial equations.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the implications of the condition a + b + c = 0 and explore various algebraic manipulations, such as substituting c = -a-b and expanding both sides of the equation. Some express uncertainty about the validity of the equation based on numerical tests with specific values for a, b, and c.

Discussion Status

The discussion is ongoing, with participants exploring different algebraic approaches to prove the equation. Some have provided guidance on how to manipulate the equation, while others question the validity of the original statement based on their numerical examples.

Contextual Notes

There is a noted emphasis on the condition a + b + c = 0, which is central to the problem. Some participants express confusion regarding the relationship between the two sides of the equation when specific values are substituted.

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Homework Statement



If a + b + c = 0, then show that
6(a^5 + b^5 + c^5) = 5(a^3 + b^3 + c^3)(a^2 + b^2 + c^2)

Homework Equations



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The Attempt at a Solution


Since a+b+c=0 then a^3 + b^3 + c^3=3abc .
But then what? I've no idea , Please help.
 
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Im sorry to say, but none of these equations work, they are not equal so they have no solutions.

I did a quick test by putting numbers in for a b and c. Being 2,3,4 the first part 6(a^5+b^5+c^5) = 5(a^3+b^3+c^3)(a^2+b^2+c^2) using the numbers i offered earlier. It comes to 7794=14355.

The second equation comes to 99=72
 
Vacrin said:
Im sorry to say, but none of these equations work, they are not equal so they have no solutions.

I did a quick test by putting numbers in for a b and c. Being 2,3,4 the first part 6(a^5+b^5+c^5) = 5(a^3+b^3+c^3)(a^2+b^2+c^2) using the numbers i offered earlier. It comes to 7794=14355.

The second equation comes to 99=72
Please read the question carefully. It says that the above holds only if a+b+c=0 and that is what I want to prove.
 
Well, that equation has quite a few solutions, wouldn't you need to solve for them all? Or does mater in the equations given below?
 
Vacrin said:
Well, that equation has quite a few solutions, wouldn't you need to solve for them all? Or does mater in the equations given below?
I do not want to solve for solutions . ( By the way the solutions are all a , b and c that sum to 0) . But I want to prove that equation when a+b+c=0.
 
I haven't tried this but the obvious thing would be to expand both sides and simplify by using the condition a + b + c = 0.
 
agoogler said:
I do not want to solve for solutions . ( By the way the solutions are all a , b and c that sum to 0) . But I want to prove that equation when a+b+c=0.

No no, i mean, solve the other given equations using things like a+b=-c
 
agoogler said:
Please read the question carefully. It says that the above holds only if a+b+c=0 and that is what I want to prove.

Put c = -a-b on both sides and expand both sides.
 
Ray Vickson said:
Put c = -a-b on both sides and expand both sides.
Thanks a lot !
After expanding I get LHS = -30 a^4 b-60 a^3 b^2-60 a^2 b^3-30 a b^4
RHS= -30 a^4 b-60 a^3 b^2-60 a^2 b^3-30 a b^4
LHS=RHS
Q.E.D.
 

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