Given function  .

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

\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \

\ x \	1	\ 6 \	4	\ 4 \
\ 1 \	1	\   3 \	3	\ 1 \
\ 2 \	1	\ 2 \	2	\ 0 \
\ 3 \	1	\ 1 \	3	\ 5 \
\ 4 \	1	\   0 \	6	\ 20 \

\

Above table one zero at x = 2, the depressed polynomial of this zero, is quadratic.

The quadratic equation is .

The function has one real zero at x = 2 and two imaginary roots.

.

The solution is x = 2, two imaginary roots .