\[\boxed{\text{186.}\text{\ }\text{ОК\ ГДЗ\ -\ домашка\ на\ 5}}\]
\[\textbf{а)}\ f(x);\ \ g(x) - четные\ \]
\[функции.\]
\[f( - x) = f(x);\ \ g( - x) = g(x)\]
\[y( - x) = f( - x) + g( - x) =\]
\[= f(x) + g(x) = y(x).\]
\[\textbf{б)}\ f(x);g(x) - нечетные\ \]
\[функции.\]
\[f( - x) = - f(x);g( - x) = - g(x)\]
\[y( - x) = - f(x) - g(x) =\]
\[= - \left( f(x) + g(x) \right) = - y(x).\]
\[Что\ и\ требовалось\ доказать.\]