=（1-3+3-5+5-7+7-9+9）+（1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72+1/90）
=1+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
=2-1/10
=19/10
...4又19\/20+5又1\/30-6又41\/42+7又1\/56-8又71\/72+9又1\/90的值...
1、1又1\/2-2又5\/6+3又1\/12-4又19\/20+5又1\/30-6又41\/42+7又1\/56-8又71\/72+9又1\/90 =（1-3+3-5+5-7+7-9+9）+（1\/2+1\/6+1\/12+1\/20+1\/30+1\/42+1\/56+1\/72+1\/90 =1+（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...
数学1又2分之1-2又6分之5-3又12分之1-4又20分之9+5又30分之1-6又42分...
裂项法：1又1\/2-2又5\/6+3又1\/12-4又19\/20+5又1\/30-6又41\/42+7又1\/56-8又71\/72+9又1\/90 =2-1\/2-3+1\/6+3+1\/12-5-1\/20+5+1\/30-7+1\/42+7+1\/56-9+1\/72+9+1\/90 =（2-3+3-5+5-7+7-9-9）+（-1\/2+1\/6+1\/12+1\/20+1\/30+1\/42+1\/56+1\/72+1\/90...
1又1\/2-2又5\/6+3又1\/12-4又19\/20+5又1\/30-6又41\/42+7又1\/56-8
+(1\/2+1\/6+1\/12+1\/20+1\/30+1\/42+1\/56+1\/72+1\/90)=1+(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+1-1\/10 =1又9\/10
1又1\/2-2又5\/6+3又1\/12-4又19\/20+5又1\/30-6又41\/42+7又1\/56-
＝2-1／10＝19／10
...1又1\/2-2又5\/6+3又1\/12-4又19\/20-5又1\/30+6又41\/42-7又1\/56+8又...
1又1\/2-2又5\/6+3又1\/12-4又19\/20+5又1\/30-6又41\/42+7又1\/56-8又71\/72+9又1\/90 =(1+1\/2)+(-3+1\/6)+(3+1\/12)+(-5+1\/20)+(5+1\/30)+(-7+1\/42)+(7+1\/56)+(-9+1\/72)+(9+1\/90)=1-3+3-5+5-7+7-9+9+1\/2+1\/6+1\/12+1\/20+1\/30+1\/42+1\/...
1又1\/2-2又5\/6+3又1\/12-4又19\/20-5又1\/30+6又41\/42-7又1\/56+8又71\/7...
1 又1\/2-2又5\/6+3又1\/12-4又19\/20-5又1\/30+6又41\/42-7又1\/56+8又71\/72-9 又1\/90 =(1-2+3-4-5+6-7+8-9)+(1\/2-5\/6+1\/12-19\/20-1\/30+41\/42-1\/56+71\/72-1\/90)=-9+(1\/2-1+1\/6+1\/12-1+1\/20-1\/30+1-1\/42-1\/56+1-1\/72-1\/90)=-9+(1-1\/...
1又2分之1-2又6分之5+3又12分之1-4又20分之19+5又30分之1-6又42分之...
原式=(1+1\/2)-(3-1\/6)+(3+1\/12)-(5-1\/20)+...+(9+1\/90)=(1-3+3-5+5-7+7-9+9)+(1\/2+1\/6+1\/20+...+1\/90)=1+(1-1\/2+1\/2-1\/3+...+1\/9-1\/10)=1+(1-1\/10)=1.9 可追问，望采纳
求教解题过程! 1又1\/2-2又5\/6+3又1\/12-4又19\/20+5又1\/30-6又14\/42
比如7又1\/90=7+1\/9×10=7+1\/9-1\/10
...4又19\/20+5又1\/30-6又41\/42+7又1\/56-8又71\/72+9又1\/90=
1½-2又5\/6+3又1\/12-4又19\/20+5又1\/30-6又41\/42+7又1\/56-8又71\/72+9又1\/90 =1+½-3+1\/6+3+1\/12-5+1\/20+5+1\/30-7+1\/42+7+1\/56-9+1\/72+9+1\/90 =1+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+9又1\/90 =(1+2+3+……+9）+（1\/2+1\/6+1\/12+……+1\/90)=(1+9)×9÷2+(1-1\/2+1\/2-1\/3+1\/3-1\/4+……+1\/9-1\/10)=45+(1-1\/10)=45.9 ...
