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MathNet 2015-part-07 — 185 problems (EN–VI) Question 172

Math Olympiad Vault · MathNet 2015-part-07 — 185 problems (EN–VI)

Question 172

Find the smallest positive integer $n$ such that there exist $n$ real numbers $a_1, a_2, \dots, a_n$ satisfying the following conditions:
i) $a_1 + \dots + a_n \gt 0$;
ii) $a_1^3 + \dots + a_n^3 \lt 0$; and
iii) $a_1^5 + \dots + a_n^5 \gt 0$.