Here we go:
P(x)=x4 - 2x3 - 13x2 - 10x
P(x) obviously = 0 when x = 0, so there is one of the real zeros. (x = 0)
P(x) can be factored into: x(x -5 )(x + 1)(x + 2) from which it is obvious that x = 5, x = -1 and x = -2 are also real zeros of P(x).
Dalia, when confronted by a situation like this, oftentimes the best thing you can do is to try to graph the equation. Here is a splendid website to which you can go to graph functions very easily:
This graphing calculator is free of charge and can make your life a whole lot easier.