I would like to verify if cubic functions always have the following pattern

.

And also, does it always have a positive-negative-positive-negative or negative-positive-negative-positive pattern.

These facts are essential to help me solve inequalities with cubic polynomials. Eg. x(x+1)(x-1)<0.

As long as I establish the sign before 1 root. I can deduce the pattern, hence saving much of my time.

I need at least 3 experts to verify.