⑴9（x-y）2-25=（3x-3y+5)(3x-3y-5)⑵（x2-y）2-（2y-2）2=(x2-y+2y-2)(x2-y-2y+2)=(x2+y-2)(x2-3y+2)⑶（a2-2b）2-（1-2b)2=(a2-2b+1-2b)(a2-2b-1+2b)=(a2-4b+1)(a2-1)=(a2-4b+1)(a-1)(a+1)