(1)(3-a+2b+c)(3+a-2b+c)=[(3+c)-(a-2b)][(3+c)+(a-2b)]
=(3+c)^2-(a-2b)^2
=9+6c+c^2-a^2+4ab-4b^2
(2)利用多项式乘法展开
(3-a+2b+c)(3+a-2b+c)=9+3a-6b+3c-3a-a^2-2ab-ac+6b+2ab-4b^2+2bc+3c+ac-2bc+c^2
=9+6c+c^2-a^2+4ab-4b^2
(1)(3-a+2b+c)(3+a-2b+c)=[(3+c)-(a-2b)][(3+c)+(a-2b)]
=(3+c)^2-(a-2b)^2
=9+6c+c^2-a^2+4ab-4b^2
(2)利用多项式乘法展开
(3-a+2b+c)(3+a-2b+c)=9+3a-6b+3c-3a-a^2-2ab-ac+6b+2ab-4b^2+2bc+3c+ac-2bc+c^2
=9+6c+c^2-a^2+4ab-4b^2