Toán Lớp 7: Tìm các cặp số nguyên (x; y) sao cho: xy – x + 2(y – 1) = 2
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Toán Lớp 7: Tìm các cặp số nguyên (x; y) sao cho: xy – x + 2(y – 1) = 2
Comments ( 2 )
=>x.(y-1)+2.(y-1)=2
=>(x+2)(y-1)=2
Ta có:
2=1.2=2.1=(-1).(-2)=(-2).(-1)
Ta có bảng sau:
$\begin{array}{|c|c|}\hline x+2&1&2&-1&-2\\\hline y-1&2&1&-2&-1\\\hline x&-1&0&-3&-4\\\hline y&3&2&-1&0\\\hline\end{array}$
Vậy (x;y)\in{(-1;3);(0;2);(-3;-1);(-4;0)}