Докажите рождество (a+b+c)^2+b^2-2ac=(a+b)^2+(b+c)^2

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