Giúp e vs ạ. E đang cần gấp ạ

` a, -1/5 +5/7-7/9+9/11-11/13-13/15+11/13-9/11+7/9-5/7`

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

`=-1/5 +0-0+0-0-13/15`

`=-1/5-13/15`

`=(-3-13) / 15`

`=-16/15`

`b, -1/3 +3/4-4/5+5/6-6/7-7/8+6/7-5/6+4/5-3/4`

`=-1/3+(3/4-3/4)-(4/5-4/5)+(5/6-5/6)-(6/7-6/7)-7/8`

`=-1/3-7/8`

`=-8/24 - 21/24=-29/24`