`x^2+y^2-x^2y^2+xy-x-y`
`= (x^2-x^2y^2)+(y^2-y)+(xy-x)`
`= -x^2(y^2-1) +y(y-1)+x(y-1)`
`= -x^2(y-1)(y+1)+y(y-1)+x(y-1)`
`=(y-1)(x+y-x^2y-x^2)`
`=(y-1)[(x-x^2)+(y-x^2y)]`
`=(y-1)[x(1-x)+y(1-x^2)]`
`=(y-1)[x(1-x)+y(1-x)(x+1)]`
`=(y-1)(1-x)(x+xy+y)`
`=(y-1)(1-x)(y+x+xy).`