Ответ:

[tex]1 - {x}^{2} + 4xy - {4y}^{2} \\ 1 - ( {x}^{2} - 4xy + {4y}^{2} ) \\ 1 - (x - 2y {)}^{2} \\ (1 - (x - 2)) \times (1 + (x - 2y)) \\ (1 - x + 2y) \times (1 + x - 2y)[/tex]