(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.

평분산 수식: (a-b)(a+b)=a2-b2; 입방차 공식으로: (a-b)(a2+ab+b2)=a3-b3; ᄋ(a-b)(a+b)(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 답은 a2-b2 a3-b3 )(a+b)(a2+b2), (an-1+an-2b+an-3b2+.+a2bn-3+abn-2+bn-1).