1-1/2+1/6+1/12+1/20+1/30+1/42+1/36,能简便的要简便计算

1-1/2+1/6+1/12+1/20+1/30+1/42+1/56=1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8=1-1/8=7/8