(1)ax2-2ax+a=a(x2-2x+1)=a(x-1)2;(2)a2(x-y)-4b2(x-y)=(x-y)(a2-4b2)=(x-y)(a+2b)(2-2b);(3)(x+y)2+2(x+y)+1=(x+y+1)2;(4)(a2+b2)2-4a2b2=(a2+b2-2ab)(a2+b2+2ab),=(a-b)2(a+b)2.