1、完全平方原式=(x²-2x+1)²=[(x-1)²]²=(x-1)四次方2、原式=[5(a+b)]²-[2(a-b)]²=(5a+5b)²-(2a-2b)²=(5a+5b+2a-2b)(5a+5b-2a+2b)=(7a+3b)(3a+7b)