The expression is

1. We start by factorizing the equation

:

The roots of f(x) occur at the x-values that result in f(x) being equal to 0.
From the factorized representation of the function, we find that the roots are:
-3 with a multiplicity of 1,
3 with a multiplicity of 1,
0 with a multiplicity of 3
(the multiplicity indicates the exponent of each factor in the function f(x)).
2.
The behavior of f(x) at both ends aligns with that of

, known for its specific graphical shape. Refer to the attached image.
(similarly, the end behavior of a polynomial of even degree could be likened to the end behavior of

)
Thus, like the graph of

, the graph of

behaves as follows:
"As x approaches negative infinity, f(x) approaches negative infinity, and as x approaches positive infinity, f(x) approaches positive infinity. "