龙的眼睛图片:1/6+1/12+1/20+1/30+．．．+1/72

1/2+1/6+1/12+1/20+1/30 1/6+1/8+1/10+1/12+..........+1/202=? 1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72+1/90= 1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72+1/90=? “1/1/2+2/1/6+3/1/12+4/1/12+......20/1/420”怎么简算？ 计算2/1+6/1+12/1……+90/1 1/2,1/6,1/12,(),1/30 1/6+1/12+1/20+1/30+．．．+1/72 1/6 =1/( )+1/( )+1/( ) 7/12=1/？+1/？+1/？