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Trả lời:
3, a3b - ab3 + a2 + 2ab + b2
= ( a3b - ab3 ) + ( a2 + 2ab + b2 )
= ab ( a2 - b2 ) + ( a + b )2
= ab ( a - b )( a + b ) + ( a + b )2
= ( a + b )[ ab( a - b ) + a + b ]
= ( a + b )( a2b - ab2 + a + b )
4, 2x3 - 2xy2 - 8x2 + 8xy
= ( 2x3 - 2xy2 ) - ( 8x2 - 8xy )
= 2x ( x2 - y2 ) - 8x ( x - y )
= 2x ( x - y )( x + y ) - 8x ( x - y )
= ( x - y )[ 2x ( x + y ) - 8x ]
= ( x - y )( 2x2 + 2xy - 8x )
= 2x ( x - y )( x + y - 4 )
