Hộ t bài này vs a. .

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`a)`

Ta có`:``

125 <= 5^x < 625 : 1/(5^2)`

`5^3 <= 5^x < 5^4 : 1/(5^2)`

`5^3 <= 5^x < 5^6`

Do đó `3<=x<6`

Suy ra `x in {3;4;5}`

Vậy `x in {3;4;5}`

`b)`

Ta có`:`

`(-32/243).(-8/27) <= (2/3)^x < 2022^0`

`(-2/3)^5 . (-2/3)^3 <= (2/3)^x < 1`

`(2/3)^8 <= (2/3)^x < (2/3)^0`

Do đó `0>x>=8`

Suy ra `x in {1;2;3;4;5;6;7;8}`

Vậy `x in {1;2;3;4;5;6;7;8}`