不值一文的老奶奶:数学问题!!!在线等!!!

1又1/2+2又1/6+3又1/12+4又1/20+5又1/30+6又1/42+7又1/56+8又1/72
=[1+2+3+..+8]+1/2+1/6+1/12+...+1/72
=[1+8]*8/2+1/1*2+1/2*3+1/3*4+...+1/8*9
=36+1/1-1/2+1/21/3+1/3-1/4+...+1/8-1/9
=36+1-1/9
=36又8/9

第二题:
21-4/3-4/15-4/35-4/63-4/99-4/143-4/195-4/255
=21-[4/1*3+4/3*5+4/5*7+...+4/15*17]
=21-[2(1/1-1/3)+2(1/3-1/5)+2(1/5-1/7)+...+2(1/15-1/17)]
=21-2[1-1/17]
=21-2+2/17
=19又2/17

1又1/2+2又1/6+3又1/12+4又1/20+5又1/30+6又1/42+7又1/56+8又1/72
=(1+2+3+4+5+6+7+8)+(1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72)
=(1+8)*8/2+[(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)]
=36+[1-1/9]
=36又8/9

21-4/3-4/15-4/35-4/63-4/99-4/143-4/195-4/255
=21-2*(2/3+2/15+2/35+2/63+2/99+2/143+2/195+2/255)
=21-2*[(1-1/3)+(1/3-1/5)+(1/5-1/7)+(1/7-1/9)+(1/9-1/11)+(1/11-1/13)+(1/13-1/15)+(1/15-1/17)]
=21-2*[1-1/17]
=21-1又15/17
=19又2/17

(1)1又1/2+2又1/6+3又1/12+4又1/20+5又1/30+6又1/42+7又1/56+8又1/72=1+2+3+....+8+1/2+1/6+1/12....+1/72
=(1+8)*8/2+1-1/2+1/2-1/3+1/3-1/4+...+1/8-1/9
=36+1-1/9=36又8/9
(2)
21-4/3-4/15-4/35-4/63-4/99-4/143-4/195-4/255
=21-4(1/3+1/15+1/35+1/63+1/99+1/143+1/195+1/255)
=21-8(1-1/3+1/3-1/5+1/5-1/7+1/7-1/9+.....1/15-1/17)
=21-8(1-1/17)=21-128/17=14又9/17
肯定对啊

332/9
325/17

332/9
325/17

1.36又2520分之2241