a+b+c=0,2a+2b+2c+2ab+2bc+2ac=?
问题描述:
a+b+c=0,2a+2b+2c+2ab+2bc+2ac=?
答
2a+2b+2c+2ab+2bc+2ac
你要问的大约是
aa+bb+cc+2ab+2bc+2ac=吧
aa+bb+cc+2ab+2bc+2ac=(a+b+c)(a+b+c)=0