计算(a+b+c)^2+(a+b-c)^2+(a-b+c)^2+(b-a+c)^2

问题描述:

计算(a+b+c)^2+(a+b-c)^2+(a-b+c)^2+(b-a+c)^2

=a^2+b^2+c^2+2ab+2bc+2ac+a^2+b^2+c^2+2ab-2bc-2ac+a^2+b^2+c^2-2ab-
2bc+2ac+a^2+b^2+c^2-2ab-2ac+2bc
=4a^2+4b^2+4c^2