x²-2xy+y²-xz+yz

=(x²-2xy+y²)-(xz-yz)

=(x-y)²-z(x-y)

=(x-y)(x-y-z)

HT

x² -2xy + y² -xz +yz

= ( x-y)² - ( xz -yz )

= ( x -y )² -z( x -y )

= ( x-y )( x-y-z )

* Sxl

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x² - y² + 2yz - z²

= x² - ( y² -2yz + z² )

= x² - ( y-z )²

= ( x-y +z ) ( x+y -z)

x² - y² + 2yz - z²

= x² - ( y² - 2yz + z² )

= x² - ( y - z )²

= ( x -y + z )( x + y - z )

x² - 6xy - 25z² + 9y²

= ( x² - 6xy + 9y² ) - 25z²

= ( x - 3y ) ² - ( 5z)²

= ( x -3y - 5z ) ( x -3y + 5z )

x² - 6xy - 25z² + 9y²

= ( x² - 6xy + 9y² ) - 25z²

= ( x - 3y )² - ( 5z )²

= ( x - 3y - 5z )( x - 3y + 5z )

#TNQ

3x² - 6xy + 3y² - 12z² 

 = 3(x² - 2xy + y² - 4z²) 

= 3[(x - y)²  - (2z)²]

= 3(x - y - 2z)(x - y + 2z) 

\(x^2-2xy+y^2-\left(2z\right)^2\)

\(=\left(x-y\right)^2-\left(2z\right)^2\)

\(=\left(x-y-2z\right)\times\left(x-y+2z\right)\)

XIN TiiCK

1, \(\left(\frac{x^2-3x}{x^2-9}-1\right):\left(\frac{9-x^2}{x^2+x-6}-\frac{x-3}{2-x}-\frac{x-2}{x+3}\right)\)ĐK : \(x\ne-3;2\)

\(=\left(\frac{x}{x+3}-1\right):\left(\frac{9-x^2+\left(x^2-9\right)-\left(x-2\right)^2}{\left(x+3\right)\left(x-2\right)}\right)\)

\(=\left(\frac{3}{x+3}\right):\left(\frac{9-x^2+x^2-9-x^2+4x-4}{\left(x+3\right)\left(x-2\right)}\right)\)

\(=\frac{3}{x+3}:\frac{-x^2+4x-4}{\left(x+3\right)\left(x-2\right)}=\frac{3}{x+3}:\frac{2-x}{x+3}=\frac{3}{2-x}\)