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x2-4x+( )=( )2,( )+2ay+1=( )2.
下列从左到右的变形中,是分解因式的是
A.(x+2)(x-2)=x2-4
B.12a2b=3a·4ab
C.4x2-8x-1=4x(x-2)-1
D.2ax-2ay=2a(x-y)