1.原式=(a-b)(a-b-1)2.原式=(2m)²-(m+n)²=(2m+m+n)(2m-m-n)=(3m+n)(m-n)3.原式=xy(4x²+4xy+y²)=xy(2x-y)²4.原式=(x-y)²-3²=(x-y+3)(x-...