Question

Tìm x,y thuộc Z biết x-y+2xy=3

Answer 1

<=> \(x=\frac{3-y}{1+2y}\)

Để x, y\(\in\)Z\(1+2y\in\text{Ư}_5\)hì \(\frac{3-y}{1+2y}\in Z\)

<=>\(3-y⋮1+2y\)

<=>\(-1-2y-5⋮1+2y\)

<=>\(1+2y\in\text{Ư}\)5

<=>\(1+2y\in\text{{}\text{ }1;-1;5;-5\)

<=>\(2y\in\text{{}0;-2;4;-6\)<=>\(y\in\text{{}0;-1;2;-3\)=>x=...

Answer 2

sao x lại bằng 3-x/1+2y vậy bạn

Answer 3

Ta thấy \(x-y+2xy=3\Rightarrow x\left(1+2y\right)=3+y\Rightarrow x=\frac{3+y}{1+2y}\)

\(x\in Z\Rightarrow2x\in Z\). Ta có \(2x=\frac{6+2y}{1+2y}=\frac{1+2y+5}{1+2y}=1+\frac{5}{1+2y}\)

\(\Rightarrow1+2y\inƯ\left(5\right)=\left\{-5;-1;1;5\right\}\)

\(y\in\left\{-3;-1;0;2\right\}\)

Với y = -3, \(x=0\)

Với y = -1, \(x=-2\)

Với y = 0, x = 3

Với y = 2, x = 1.