[tex](3 x^{2} +2y-1)-[(- y^{2} - x-y-1)+(2 y^{2} +x+y-4)]-[-( x^{2} - y^{2} -y+1)-( x^{2} + y^{2}-x-y+1 )] =[/tex][tex]3 x^{2} +2y-1-(- y^{2} -x-y-1+2 y^{2} +x+y-4)-[/tex][tex](- x^{2} + y^{2} +y-1- x^{2} - y^{2} +x+y-1 ) =[tex]3 x^{2} +2y-1+ y^{2} +x+y+1-2 y^{2} -x-y+4+ x^{2} - y^{2} -y+1+ x^{2} [/tex][tex]+ y^{2} -x-y+1=5 x^{2} - y^{2} -x+6[/tex]