A cura di: Francesco Speciale

Svolgimento:

$7ab=a^2+b^2$
$ab=1/9(a^2+b^2+2ab)=1/9(a+b)^2$
$sqrt(ab)=1/3(a+b)$
$log(sqrt(ab))=log(a+b)/3$
$1/2(loga+logb)=log(a+b)/3$