\[\boxed{\text{823.}\text{\ }еуроки - ответы\ на\ пятёрку}\]
\[\textbf{а)}\ (a - b)^{2} = (b - a)²\]
\[a^{2} - 2ab + b^{2} = b^{2} - 2ab + a^{2}\]
\[(a - b)^{2} = (b - a)²\]
\[\textbf{б)}\ \ ( - a - b)^{2} = (a + b)²\]
\[( - a)^{2} + 2 \cdot ( - a) \cdot ( - b) +\]
\[+ ( - b)^{2} = a² + 2ab + b²\]
\[a² + 2ab + b² = a^{2} + 2ab + b^{2}\]
\[( - a - b)^{2} = (a + b)²\]