1+1/(√2)+1/(√3)+……+1/(√n)=2[1/2+1/(2√2)+1/(2√3)+……+1/(2√n)]<2{1/[(√1)+0] + 1/[(√2)+(√1)] + 1/[(√3)+(√2)]+……+ 1/[(√n)+(√n-1)]} =2[1+(√2)-1+(√3)-(√2)+……+(√n)-(√n-1)] =2√n
