分解因式：4(x²-y²)-(x+y)²-4(x-y)²

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分解因式：4(x²-y²)-(x+y)²-4(x-y)²

4(x²-y²)-(x+y)²-4(x-y)²
=4x²-4y²-x²-2xy-y²-4x²+8xy-4y²
=-x²+6xy-9y²
=-(x-3y)²

4( x" - y" ) - ( x + y )" - 4( x - y )"
= 4( x - y )( x + y ) - ( x + y )" - 4( x - y )"
= - [ ( x + y )" - 4( x + y )( x - y ) + 4( x - y )" ]
= - [ ( x + y ) - 2( x - y ) ]"
= - ( x ...

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4( x" - y" ) - ( x + y )" - 4( x - y )"
= 4( x - y )( x + y ) - ( x + y )" - 4( x - y )"
= - [ ( x + y )" - 4( x + y )( x - y ) + 4( x - y )" ]
= - [ ( x + y ) - 2( x - y ) ]"
= - ( x + y - 2x + 2y )"
= - ( 3y - x )"
= - ( x - 3y )"

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