(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.

∵ from the square difference formula: (a-b) (a + b) = A2-B2; (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, so the answer is: A2-B2 a3-b3) (a + b) (A2 + B2), (an-1 + an-2b + an-3b2 + +a2bn-3+abn-2+bn-1).