Tìm a,b ∈ 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)