Question

[Đỗ Thị Như Quỳnh]

Tìm các số nguyên x,y thỏa mãn :

a, x+ y + xy = 6 

b, 2x + y - 2xy - 8 = 0

c, x - 4y + xy - 1 = 0

Answer 1

[Nguyễn Anh Kim Hân]

a) x + y +xy = 6

y( 1 + x ) + x + 1 = 7

( x + 1 ) ( y + 1 ) = 7

x+1	-7	-1	1	7
y+1	-1	-7	7	1
x	-8	-2	0	6
y	-2	-8	6	0

b) 2x + y - 2xy - 8 = 0

2x ( 1 - y ) - ( 1 - y ) - 7 = 0

( 1 - y ) ( 2x - 1 ) = 7

2x - 1	-7	-1	1	7
1 - y	-1	-7	7	1
x	-3	0	1	4
y	2	8	-6	0

c) x - 4y + xy - 1 = 0

x( 1 + y ) -4( 1 + y ) + 3 = 0

( 1 + y ) ( x- 4 ) = 3

x- 4	-3	-1	1	3
1 + y	-1	-3	3	1
x	1	3	5	7
y	-2	-4	2	0