202) Ta có: $\prod \left ( a+\frac{1}{a+1} \right )=\prod \left ( \frac{a^{2}}{a+1}+1 \right )=\prod \left (\frac{a^{2}}{a+1}+\frac{a+1}{4}-\frac{a}{4}+\frac{3}{4} \right )\geq \prod \left( a - \frac{a}{4}+\frac{3}{4}\right )=\frac{27}{64}\prod \left (a+1 \right )\geq \frac{27}{64}\cdot 8\prod \left (\sqrt{a} \right )\geq \frac{27}{8}$
Dấu "=" xảy ra khi và chỉ khi a=b=c=1