5. Сократите дробь \(\frac{2(x-y)}{y-x}\).

Поскольку \(y-x=-(x-y)\), при \(x\ne y\):

\[\frac{2(x-y)}{y-x}=\frac{2(x-y)}{-(x-y)}=-2.\]

Ответ: \(-2\), при \(x\ne y\).