\[\boxed{\text{104.\ }\text{ОК\ ГДЗ\ -\ домашка\ на\ 5}}\]
\[\textbf{а)}\ f(x) = x + \frac{1}{x}\]
\[f( - x) = - x - \frac{1}{x} =\]
\[= - \left( x + \frac{1}{x} \right) = - f(x)\]
\[функция\ нечетная.\]
\[\textbf{б)}\ f(x) = 2x^{3} - x\]
\[f( - x) = 2 \cdot ( - x)^{3} - ( - x) =\]
\[= - 2x^{3} + x = - \left( 2x^{3} - x \right) =\]
\[= - f(x)\]
\[функция\ нечетная.\]