1. The problem is to prove the identity $$a^3 + b^3 + c^3 = 3abc$$ under certain conditions.
2. This identity is true if and only if $$a + b + c = 0$$. This is a key condition to remember.
3. The formula for the sum of cubes with three variables is:
$$a^3 + b^3 + c^3 - 3abc = (a + b + c)(a^2 + b^2 + c^2 - ab - bc - ca)$$
4. If $$a + b + c = 0$$, then the right side becomes:
$$(0)(a^2 + b^2 + c^2 - ab - bc - ca) = 0$$
5. Therefore, under the condition $$a + b + c = 0$$, we have:
$$a^3 + b^3 + c^3 - 3abc = 0$$
which implies
$$a^3 + b^3 + c^3 = 3abc$$
6. This completes the proof. The key takeaway is that the identity holds when the sum of the three variables is zero.
7. To summarize:
- Start with the known factorization.
- Apply the condition $$a + b + c = 0$$.
- Simplify to get the desired equality.
Cube Sum Identity
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