Tìm a,b ∈ `ZZ` biết ( a - 2 ) . b = -5

2 câu trả lời

Đáp án:

`( a - 2 ) . b = -5`

Do: `a,b ∈ ZZ`

`→ a - 2; b ∈ ZZ` 

`→ a - 2; b ∈ Ư_{(-5)} = {-1;1;5;-5}`

Lập bảng giá trị

            \begin{array}{|c|c|c|}\hline \text{a - 2}&\text{-1}&\text{1}&\text{-5}&\text{5}\\\hline \text{b}&\text{5}&\text{-5}&\text{1}&\text{-1}\\\hline \text{a}&\text{1}&\text{3}&\text{-3}&\text{7}\\\hline\end{array}

Vậy `(a,b) = (1,5);(3; -5); (-3; 1); (7; -1)`

$#dariana$

`( a - 2 ) . b = -5`

Vì : `a,b ∈ ZZ`

`=> a - 2; b ∈ ZZ` 

`=> a - 2; b ∈ Ư(-5) = {±1;±5}`

Ta có bảng :
\begin{array}{|c|c|c|}\hline \text{a - 2}&\text{-1}&\text{1}&\text{-5}&\text{5}\\\hline \text{b}&\text{5}&\text{-5}&\text{1}&\text{-1}\\\hline \text{a}&\text{1}&\text{3}&\text{-3}&\text{7}\\\hline\end{array}

Vậy `(a,b) = (1,5);(3; -5); (-3; 1); (7; -1)`


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