hlep meee cứu vs ạk'^'

Đáp án `+` Giải thích các bước giải:

a) `-12/7 + 25/7 = (-12 + 25)/7 = 13/7`

b) `8/27 - 17/27 = (8 - 17)/27 = -7/27`

c) `-2/9 . 3/14 : (-5)/21 `

`= -1/3 . 1/7 . (-21)/5`

`= -1/21 . (-21)/5`

`= 1/5.`

d) `-3/7 . 4/19 - 3/7 . 15/19 + 3/7`

`= 3/7 . (-4)/19 - 3/7 . 15/19 + 3/7`

`= 3/7 . (-4/19 - 15/19 + 1)`

`= 3/7 . (-1 + 1)`

`= 3/7 . 0 = 0.`

e) `3/(1 . 4) + 3/(4 . 7) + 3/(7 . 10) + 3/(10 . 13) + 3/(13 . 16)`

`= 1 - 1/4 + 1/4 - 1/7 + 1/7 - 1/10 + 1/10 - 1/13 + 1/13 - 1/16`

`= 1 - 1/16`

`= 15/16.`