Question

\(\left(a+b+c\right)^2\)

Answer 1

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

Answer 2

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

Answer 3

\(\left(a+b+c\right)^2\)

\(=\left[\left(a+b\right)+c\right]^2\)

\(=\left(a+b\right)^2+2\left(a+b\right)c+c^2\)

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

\(=a^2+b^2+c^2+2ab+2bc+2ca\)