Question

giúp mik bài 7

 

Answer 1

`a)1/10 - 1/100 - 1/1000 - 1/10000 - 1/100000`

`= -10/100 - 1/100 - 1/1000 - 1/10000 - 1/100000`

`= -110/1000 - 1/1000 - 1/10000 - 1/100000`

`= -111/1000 - 1/10000 - 1/100000`

`= -1110/10000  - 1/10000 - 1/100000`

`= -11110/100000 - 1/100000`

`= -11111/100000`

_______________

`b)1/3-3/5+5/7-7/9+9/11-11/13+13/15+11/13-9/11+7/9-5/7+3/5-1/3`

`=1/3-1/3+5/7-5/7+9/11-9/11+13/15+11/13-11/13+7/9-7/9+3/5-3/5`

`=(1/3-1/3)+(5/7-5/7)+(9/11-9/11)+13/15+(11/13-11/13)+(7/9-7/9)+(3/5-3/5)`

`=13/15`