1×2/1+2×3/1+3×4/4+.+49×50/1

问题描述:

1×2/1+2×3/1+3×4/4+.+49×50/1
简便

原式=1-1/2+1/2-1/3+...+1/49-1/50
=1-1/50
=49/50