2/(2²-1)+2/(4²-1)+2/(6²-1)+2/(8²-1)+2/(10²-1)+2/(12²-1)=2/[(2-1)×(2+1)]+2/[(4-1)×(4+1)]+2/[(6-1)×(6+1)]+2/[(8-1)×(8+1)]+2/[(10-1)×(10+1)]+2/[(12-1)×(12+1)]=2/(1×3)...