Odpowiedzi

2009-12-01T16:16:24+01:00
3xy(2xy-1)-(2xy+3)²-xy (xy-15) =
6x²y²-3xy-(4x²y²+9+12xy)-x²y²+15xy=
6x²y²-3xy-4x²y²-9-12xy-x²y²+15xy = x²y²-9