Ответ:
\[а)\ f(x) > 0\ \ \ при\ \ x < - 4\ \ \ \]
\[и\ \ x > - 1.\]
\[б)\ f(x) > 0\ \ \ \]
\[при\ \ - 1 < \ x < 3.\]
\[в)\ f(x) > 0\ \ \ \]
\[при\ \ x < 2,\ \ \ 3 < x < 4.\]
\[а)\ f(x) > 0\ \ \ при\ \ x < - 4\ \ \ \]
\[и\ \ x > - 1.\]
\[б)\ f(x) > 0\ \ \ \]
\[при\ \ - 1 < \ x < 3.\]
\[в)\ f(x) > 0\ \ \ \]
\[при\ \ x < 2,\ \ \ 3 < x < 4.\]