Question

x.y - 3x - 3y = 0

Answer 1

Ta có xy-3x-3y=0

\(\Leftrightarrow xy-3x-3y+9=9\)

\(\Leftrightarrow x\left(y-3\right)-3\left(y-3\right)=9\)

\(\Leftrightarrow\left(x-3\right)\left(y-3\right)=9\)

Do đó ta lập bảng

x-3=	y-3=	x=	y=
1	9	4	12
9	1	12	4
-1	-9	2	-6
-9	-1	-6	2
-3	-3	0	0
3	3	6	6

Vậy cặp (x;y) là (4;12);(12;4);(2;-6);(-6;2);(0;0);(6;6)

Answer 2

\(xy-3x-3y=0\)

\(\Leftrightarrow\left(x-3\right)y-3y+9=9\)

\(\Leftrightarrow\left(x-3\right)y-3\left(x-3\right)=9\)

\(\Leftrightarrow\left(x-3\right)\left(y-3\right)=9\)