2/1x2x3+2/2x3x4+2/3x4x5+2/4x5x6+...+2/98x99x100=

问题描述:

2/1x2x3+2/2x3x4+2/3x4x5+2/4x5x6+...+2/98x99x100=

原式=(1/1*2-1/2*3)+(1/2*3-1/3*4)+……(1/98*99-1/99*100)
=1/1*2-1/99*100
=49499/99000