Question

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

Answer 1

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

= a sq.+b sq.+ c sq.+ 2ab+2 bc+2ac+a sq. + b sq.+ c sq. + 2 ab -2ac-2 bc+a sq. + b sq. + c sq. -2 ab - 2bc + 2 ac

=3 a sq.+ 3 b sq. + 3 c sq. +ab - bc + ac