a>0=> a+1/a>=2=> a^2+1/a^2>=2s=a+1/a-√(a^2+1/a^2)=> [a+1/a+√(a^2+1/a^2)]s=[a+1/a-√(a^2+1/a^2)][a+1/a-√(a^2+1/a^2)]=(a+1/a)^2-(a^2+1/a^2)=2s=2/[a+1/a+√(a^2+1/a^2)]
