1/1×2+1/2×3+1/3×4+……+1/2013×2014=1-1/2+1/2-1/3+1/3-1/4+...........+1/2013-1/2014=1-1/2014=2013/2014
=1-1/2+1/2-1/3+1/3-1/4+....1/2013-1/2014=1-1/2014=2013/2014
