[Keehlzver]

Cannot type Thai(New Window screwed me up)
$16$ $\sum \frac{a}{\sqrt{a^2+8bc}}$

Solution

$(\sum\frac{a}{\sqrt{a^2+8bc}})^2\geq\frac{(a+b+c)^3}{a^3+b^3+c^3+24abc}\geq1$ iff $(a+b+c)^3\geq a^3+b^3+c^3+24abc$ iff $(a+b)(b+c)(c+a)\geq 8abc$ Obviously true.

And $17$ I don't know Log Please give me a hint