Đáp án`+`Giải thích các bước giải:

`1) 1/2 - (2/3)^9 : (2/3)^7 + 5/6`

`= 1/2 - (2/3)^(9 - 7) + 5/6`

`= 1/2 - 4/9 + 5/6`

`= 8/9`

`2) (3/7)^3 . (7/6)^3 + 2/3 : (4/3)^2`

`= 27/343 . 343/216 + 2/3 : 16/9`

`= 1/8 + 3/8`

`= 1/2`

`3) -4/7 : 9/14 + (4/3)^4 : (4/3)^2`

`= -4/7 . 14/9 + (4/3)^(4 - 2)`

`= -8/9 + 16/9`

`= 8/9`

`4) (-4/3 + 1) - (-2/3)^21 : (-2/3)^19`

`= -1/3 - (-2/3)^(21 - 19)`

`= -1/3 - (-2/3)^2`

`= -1/3 - 4/9`

`= -7/9`

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