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標題:

數學題(中二)

發問:

因式分解 m^3+27(m-1)^3 a^3-b^3-a^2+b^2

最佳解答:

m^3 + 27 ( m – 1 )^3 = m^3 + [ 3 ( m – 1 ) ]^3 = m^3 + ( 3m – 3 )^3 = [ m + ( 3m – 3 ) ] [ m^2 – m ( 3m – 3 ) + ( 3m – 3 )^2 ] = ( 4m – 3 ) ( m^2 – 3m^2 + 3m + 9m^2 – 18m + 9 ) = ( 4m – 3 ) ( 7m^2 – 15m + 9 ) a^3 – b^3 – a^2 + b^2 = ( a^3 – b^3 ) – ( a^2 – b^2 ) = ( a – b ) ( a^2 + ab + b^2 ) – ( a + b ) ( a – b ) = ( a – b ) [ a^2 + ab + b^2 – ( a + b ) ] = ( a – b ) ( a^2 + ab + b^2 – a – b )

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