(1)、3x(x-y)-6y(x-y)
=2(x-y)(x-2y)
(2)、ax^5-ax^3
=ax^3(x^2-1)
=ax^3(x+1)(x-1)
(3)、(x^2+4)^4-16x^2
=(x^2+4+4x)(x^2+4-4x)
=(x+2)^2(x-2)^2
(4)、(a+b)^2-6(a+b)+9
=(a+b-3)^2
(5)、-1/2x^2+xy-1/2y^2
=-1/2(x^2-2xy+y^2)
=-1/2(x-y)^2
(6)、(x^2+16y^2)-64x^2y^2
这里漏了个平方
(x^2+16y^2)^2-64x^2y^2
=(x^2+16y^2+8xy)(x^2+16y^2-8xy)
=(x+4y)^2(x-4y)^2