Question 156
Let $a$, $b$, $c$, $d$ be arbitrary real numbers satisfying $a + b + c + d = 0$. Prove that
$$
1296(a^7 + b^7 + c^7 + d^7)^2 \le 637(a^2 + b^2 + c^2 + d^2)^7.
$$
$$
1296(a^7 + b^7 + c^7 + d^7)^2 \le 637(a^2 + b^2 + c^2 + d^2)^7.
$$
MathNet 2015-part-06 — 191 problems (EN–VI) Question 156
Math Olympiad Vault · MathNet 2015-part-06 — 191 problems (EN–VI)