Given function  .

The f(x) has degree 3 and three zeros.

\  x \	\   \	\   \		\   \
\ \	\   \	\ \	\ \	\ \
\ \	\ \	\ \	\ \	\ \
\ \	\ \	\ \	\ \	\ \
\ \	\ \	\ \	\ \	\ \
\ \	\ \	\ \	\ \	\ \

 Above table three zeros at .

The function have three real zeros at .

The solutions are .