Question

разложите на множетели 9-x²-2xy-y²

Answer 1

$9 - {x}^{2} - 2xy - {y}^{2} = \\ = 9 - {(x + y)}^{2} = \\ = (3 - x - y)(3 + x + y)$

Answer 2

$9 - {x}^{2} - 2xy - {y}^{2} = - (3 + x + y)(x + y - 3)$