Question

已知a+b+c=0,求a^2+b^2+c^2+2ab+2bc+2ac是多少?

Answer 1

a^2+b^2+c^2+2ab+2bc+2ac

=(a^2+b^2+2ab)+c^2+(2ac+2bc)

=(a+b)^2+2c(a+b)+c^2

=(a+b+c)^2

=0