1/(1*2)=1-1/2
1/(2*3)=1/2-1/3
.
1/1*2+1/2*3+1/3*4+…+1/1993*1994 1/3+1/15+1/35+1/63+...+1/17*19
=1-1/2+1/2-1/3+...+1/17-1/19
=1-1/19
=18/19谢谢 还有一道题1/3+1/15+1/35+1/63+...+1/17*19=1/(1*3)+1/(3*5)+...+1/(17*19)=1/2*(1-1/3+1/3-1/5+...+1/17-1/19)=1/2*(1-1/19)=1/2*18/19=9/19