# 1. Assume $a+b+c = 1$, then the inequality becomes $$\sum_{cyc}\sqrt{\frac{a}{b+1}}\leq \frac{3}{2}$$ By Cauchy-Schwarz, $$ \sum_{cyc}\sqrt{\frac{a}{b+1}} \leq \sqrt{\sum_{cyc}(a+1)} \sqrt{\sum_{cyc}\frac{a}{(b+1)(a+1)}} = 2\sqrt{\sum_{cyc}\frac{a}{(b+1)(a+1)}} $$ Let $s_2 = ab + bc + ac$, $s_3 = abc$, we have $$ \sum_{cyc}\frac{a}{(b+1)(a+1)} = \sum_{cyc}\frac{a(c+1)}{(a+1)(b+1)(c+1)}=\frac{1+s_2}{2+s_2+s_3} $$ By Schur's inequality(小蓝本不等式 pp.19, 变形II) $$ s_3 \geq \frac{4s_2 - 1}{9} $$ Plug it into the third line formula: $$ \sum_{cyc}\frac{a}{(b+1)(a+1)} \leq \frac{1+s_2}{2+s_2+\frac{4s_2-1}{9}} = \frac{9+9s_2}{17+13s_2} $$ To show $\sum_{cyc}\sqrt{\frac{a}{b+1}}\leq \frac{3}{2}$, it suffices to show $$ \frac{9+9s_2}{17+13s_2} \leq \frac{9}{16} $$ And it's simply true as $s_2\leq 1/3$. # 2. I underestimated it. It's hrad. I list some references to it: 1. https://artofproblemsolving.com/community/c4h2026588p14265546 2. https://artofproblemsolving.com/community/c6h2035758p14374093 3. https://artofproblemsolving.com/community/c6h176214p973283 4. https://artofproblemsolving.com/community/c6h205602p1131751 5. https://artofproblemsolving.com/community/c6h2027246p14272357