\(-8x^2y^2-12xy^2-4xy^2=-8x^2y^2-16xy^2\)

\(=-8xy^2\left(x+2\right)\)

-8x²y² - 12xy² - 4xy²

\(=-4xy\left(2xy+3y+y\right)\)

\(-8x^2y^2-12xy^2-4xy^2\)

\(=-4xy^2\left(2x+3+1\right)\)

\(=-4xy^2\left(2x+4\right)\)

\(=2xy\left(x^2-y^2-2y-1\right)\)

\(=2xy\left[x^2-\left(y^2+2y+1\right)\right]\)

\(=2xy\left[x^2-\left(y+1\right)^2\right]\)

\(=2xy\left(x-y-1\right)\left(x+y+1\right)\)

\(2x^3y-2xy^3-4xy^2-2xy\)

\(=2xy\left(x^2-y^2-2y-1\right)\)

\(=2xy\left[x^2-\left(y+1\right)^2\right]\)

\(=2xy\left(x-y-1\right)\left(x+y+1\right)\)

2x3y – 2xy3 – 4xy2 – 2xy

= 2xy(x2 - y2 - 2y - 1)

= 2xy[x2 - (y2 + 2y + 1)]

= 2xy[x2 - (y + 1)2 ]

= 2xy(x + y + 1)(x - y - 1)

2 x 3 y   –   2 x y 3   –   4 x y 2   –   2 x y     =   2 x y ( x 2   –   y 2   –   2 y   –   1 )     =   2 x y [ x 2   –   ( y 2   +   2 y   +   1 ) ]     =   2 x y [ x 2   –   ( y   +   1 ) 2 ]

= 2xy(x – y – 1)(x + y + 1)

Đáp án cần chọn là: A

\(a,=\left(2x-y\right)^2\\ b,=9x^2\left(x-y\right)-4\left(x-y\right)=\left(3x-2\right)\left(3x+2\right)\left(x-y\right)\\ c,=x^2+2+3x^2-6=4x^2-4=4\left(x-1\right)\left(x+1\right)\)

4xy - x² + 9 - 4y²

= -(x² - 4xy + 4y² - 9)

= -[(x² - 4xy + 4y²) - 3²]

= -[(x - 2y)² - 3²]

= -(x - 2y - 3)(x - 2y + 3)

\(\left(x+2y-4\right)\left(x+2y+4\right)\)

a: \(=x\left(x+y\right)-\left(x+y\right)=\left(x+y\right)\left(x-1\right)\)

b: \(=25-\left(x-2y\right)^2\)

\(=\left(5-x+2y\right)\left(5+x-2y\right)\)

(x+y)^2 - 5y^2

x^2- 4y^2 + 4xy

= x^2 + 4xy - 4y^2

=x^2 + 2x2y - (2y)^2

= ( x - 2y )^2

 x² - 4y² + 4xy = x² + 4xy - 4y² = - (x² - 4xy + 4y²) = - ((x² - 2x.2y + (2y)²)

= - ( x - 2y)²