1/1x3+1/2x4+1/3x5+-----+1/1998x2000=?
问题描述:
1/1x3+1/2x4+1/3x5+-----+1/1998x2000=?
答
1/2(1-1/3+1/2-1/4……+1/1998-1/2000)=1/2*(1+1/2-1/1999-1/2000
1/1x3+1/2x4+1/3x5+-----+1/1998x2000=?
1/2(1-1/3+1/2-1/4……+1/1998-1/2000)=1/2*(1+1/2-1/1999-1/2000