-Is x2 + 2xy-y2 a complete square If it can be used, does it mean it can be used? that. 4Y & # 178 / / X & # 178; - XY + Y & # 178; this should not work, right?

-Is x2 + 2xy-y2 a complete square If it can be used, does it mean it can be used? that. 4Y & # 178 / / X & # 178; - XY + Y & # 178; this should not work, right?

No, because this polynomial is a complete square only after extracting "-