\[\boxed{\text{577\ (577).\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
\[(a - b)^{2} = (b - a)^{2}\]
\[a^{2} - 2ab + b^{2} = b^{2} - 2ab + a^{2}\]
\[a^{2} - 2ab + b^{2} = a^{2} - 2ab + b^{2}.\]
\[Тождество\ доказано.\]