补充的题,可化为
1-1/2+(1/2-1/3)+(1/3-1/4)+(1/4-1/5).(1/9-1/10)=9/10
7/20/[4/5-12/13(1/2+1/3)]=7/20/(4/5-12/13*5/6)=7/20/(52/65-50/65)=7/20*65/2=91/8
补充的题,可化为
1-1/2+(1/2-1/3)+(1/3-1/4)+(1/4-1/5).(1/9-1/10)=9/10
7/20/[4/5-12/13(1/2+1/3)]=7/20/(4/5-12/13*5/6)=7/20/(52/65-50/65)=7/20*65/2=91/8