=1+2/(2^2-1)+1+2/(3^2-1)+...+1+2/(11^2-1)=10+2[1/(2^2-1)+1/(3^2-1)+...+1/(11^2-1)]=10+2{[1/(2-1)-1/(2+1)]/2+[1/(3-1)-1/(3+1)]/2+...+[1/(11-1)-1/(11+1)]/2}=10+(1/1-1/3+1/2-1/4+...+1/10-1/12)=10+(1+1/2-...