1×2分之1等于1分之1-2分之一,2乘三分之一等于2分之1-3分之一……
1/2 1/6 1/12 1/20 1/30 1/42 1/56 1/72 1/90=(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) (1/8-1/9) (1/9-1/10)=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)-(1/8-1/8)-(1/9-1/9)-1/10=1-1/10=0。 9。
1/2 1/6 1/12 1/20 1/30 1/42 1/56 1/72 1/90=(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) (1/8-1/9) (1/9-1/10)=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)-(1/8-1/8)-(1/9-1/9)-1/10=1-1/10=0。
9。收起