8+2sqrt(12)=(sqrt(x)+sqrt(y))^2, x > 0; y > 0.
8+2sqrt(12)=x+y+2sqrt(xy),
Тогда
{х+у=8;
{sqrt(xy)=sqrt(12);
{х+у=8;
{xy=12;
{x=6; {x=2
{y=2; {y=6
sqrt(8+2sqrt(12))=sqrt((sqrt(2)+sqrt(6))^2=|sqrt(2)+sqrt(6)|=sqrt(2)+sqrt(6)
{x+y=8;
Ответ: sqrt(2)+sqrt(6)