` 1) ` ` 3 \vdots 2x - 10 `
` => 2x - 10 ∈ Ư(3) = {±1 ; ±3} `
Ta có bảng:
2x - 10 | - 3 | - 1 | 1 | 3 |
2x | 7 | 9 | 11| 13|
x | `7/2` | `9/2` |` 11/2 `|`13/2`|
Vậy ` x ∈ { 7/2 ; 9/2 ; 11/2 ; 13/2 } ` thì ` 3 \vdots 2x - 10 `
` 2) ` ` (x + 2^5) . 5^{23} = 5^{25} `
` => x + 32 = 5^{2} `
` => x = 25 - 32 `
` => x = -7 `
Vậy ` x = -7 `