\[\boxed{\text{163\ (163).\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
Пояснение.
Решение.
\[\textbf{в)}\ \left( \frac{x}{y} + 1 \right)^{2} + \left( \frac{x}{y} - 1 \right)^{2} =\]
\[= \frac{x^{2}}{y^{2}} + 2\frac{x}{y} + 1 + \frac{x^{2}}{y^{2}} - 2\frac{x}{y} + 1 =\]
\[= \frac{2x^{2}}{y^{2}} + 2^{\backslash y^{2}} = \frac{2x^{2} + 2y^{2}}{y^{2}}\]
\[\textbf{г)}\ \left( \frac{p}{q} + \frac{q}{p} \right)^{2} - \left( \frac{p}{q} - \frac{q}{p} \right)^{2} =\]
\[= \frac{2pq}{\text{qp}} + \frac{2pq}{\text{qp}} = \frac{4pq}{\text{pq}} = 4\]