Look what happens if you do the multiplication of P(x):
P(x) = x^3 - 9x
This is a variation of the basic cubing function y = x^3.
The graph begins in QIII and ends in QI; in other words, if you go left the graph drops; if you go right, the graph rises (without limit, in both cases).
The distance of the two lines are 5 units apart. Sorry i can't write on computers lol. If you need help with graphs i recommend a website call Desmos, it is very helpful.