（a+1)^2-2(a+1)(a-1)+3(a-1）^2
问题描述：
（a+1)^2-2(a+1)(a-1)+3(a-1）^2
（a+1)^2-2(a+1)(a-1)+3(a-1）^2（过程要带啊),老师叫我讲，正确的
答
直接解（a+1)^2-2(a+1)(a-1)+3(a-1）^2=a^2+2a+1-2a^2+2+3a^2-6a+3=2a^2-4a+6较简便的（a+1)^2-2(a+1)(a-1)+3(a-1）^2=[(a+1)-(a-1)]^2+2(a-1)^2=4+2a^2-4a+2=2a^2-4a+6我本助人为乐而解,这里省了几步,我一般都会这...