Question 41
For all real numbers $a, b, c, d$ not exceeding $2$, prove that
$$
\frac{a^3}{b^2+4} + \frac{b^3}{c^2+4} + \frac{c^3}{d^2+4} + \frac{d^3}{a^2+4} \le 4.
$$
(Otgonbayar Uuye)
$$
\frac{a^3}{b^2+4} + \frac{b^3}{c^2+4} + \frac{c^3}{d^2+4} + \frac{d^3}{a^2+4} \le 4.
$$
(Otgonbayar Uuye)