(a-b)(a+b)=______(a-b)(a2+ab+b2)=______(a-b)______=a4-b4(a-b)______=an-bn.

(a-b)(a+b)=______(a-b)(a2+ab+b2)=______(a-b)______=a4-b4(a-b)______=an-bn.

∵由平方差公式得:(a-b)(a+b)=a2-b2;由立方差公式得:(a-b)(a2+ab+b2)=a3-b3;∴(a-b)(a+b)(a2+b2)=(a2-b2)(a2+b2)=a4-b4(a-b)(an-1+an-2b+an-3b2+…+a2bn-3+abn-2+bn-1)=a(an-1+an-2b+an-3b2+…+a2bn-3+abn-2+bn-1)-b(an-1+an-2b+an-3b2+…+a2bn-3+abn-2+bn-1)=an-bn故答案為:a2-b2 a3-b3)(a+b)(a2+b2),(an-1+an-2b+an-3b2+…+a2bn-3+abn-2+bn-1).