Tìm các số nguyên x,y sao cho x(y+1)-y=6

`x(y+1)-y=6`

`=>x(y+1)-(y+1)=6-1`

`=>(y+1)(x-1)=5`

Vì `x,y in ZZ`

`=>x-1,y+1 in ZZ`

`=>x-1,y+1 in Ư(5)={+-1,+-5}`

TH1:

`x-1=1,y+1=5`

`=>x=2,y=4(tm)`

TH2:

`x-1=5,y+1=1`

`=>x=6,y=0(tm)`

TH3:

`x-1=-1,y+1=-5`

`=>x=0,y=-6(tm)`

TH4:

`x-1=-5,y+1=-1`

`=>x=-4,y=-2(tm)`

Vậy `(x,y) in {(2,4),(6,0),(0,-6),(-4,-2)}`