perplexus.info :: Just Math : Derive a formula

Derive a formula (Posted on 2023-07-27)

Given
a+b+c=0 and abc=4

Evaluate S=a^3+b^3+c^3

See The Solution Submitted by Ady TZIDON

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Puzzle Solution

| Comment 1 of 3

a+b+c=0

Or, a+b=-c

Or, a^3+b^3+3ab(a+b)= -c^3

Or, a^3+b^3+c^3+3ab*(-c)=0

Or, a^3+b^3+c^3=3abc

Or, a^3+b^3+c^3=3*4

Or, a^3+b^3+c^3=12

QED

Posted by K Sengupta on 2023-07-27 09:12:29

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