快(10分)~~

1. 289 - x^6y^4 = 17^2 - (x^3y^2)^2 = (x^3y^2 - 17)(x^3y^2 + 17)
用a^2 - b^2 = (a + b)(a - b)

2. 27-x^3 = 3^3 - x^3 = (3-x)(3^2 + 3x + x^2)
用 a^3 - b^3 = (a - b)( a^2 + ab + b^2)

3. 16m^3+2 = 2(8m^3 + 1) = 2( (2m)^3 + 1^3 ) = 2(2m + 1)(4m^2 - 2m + 1)

用 a^3 + b^3 = (a+b) (a^2 - ab + b^2)

2007-08-28 17:21:11 補充：
(x y)(2a-3b) (x y)(2b-c) = (x y)(2a - 3b 2b - c) = (x y)(2a - b - c)先揪common factor