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