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MathNet 2023-part-03 — 191 problems (EN–VI) Question 71

Math Olympiad Vault · MathNet 2023-part-03 — 191 problems (EN–VI)

Question 71

Let $a, b, c$ be real numbers (positive, negative, or zero) such that $a^{2}+b^{2}+c^{2}=6$.

a) Determine the maximum possible value for the expression
$$
(a-b)^{2}+(b-c)^{2}+(c-a)^{2} .
$$

b) Determine the maximum possible value for the expression
$$
(a-b)^{2} \cdot(b-c)^{2} \cdot(c-a)^{2} .
$$

In both cases, describe all the triples for which the maximum is achieved.