For every natural number $n\geq{2}$ consider the following affirmation $P_n$:
"Consider a polynomial $P(X)$ (of degree $n$) with real coefficients. If its derivative $P'(X)$ has $n-1$ distinct real roots, then there is a real number $C$ such that the equation $P(x)=C$ has $n$ real,distinct roots." 
Are $P_4$ and $P_5$ both true? Justify your answer.
To determine whether the affirmations \( P_4 \) and \( P_5 \) are true, we need to analyze the given conditions for polynomials of degree 4 and 5, respectively.

1. **Case \( n = 4 \):**
   - Consider a polynomial \( P(X) \) of degree 4 with real coefficients.
   - Its derivative \( P'(X) \) is a polynomial of degree 3.
   - Given that \( P'(X) \) has 3 distinct real roots, say \( x_1 < x_2 < x_3 \).

   Since \( P'(X) \) changes sign at each of these roots, \( P(X) \) will have local extrema at \( x_1, x_2, \) and \( x_3 \). Specifically:
   - \( P(X) \) will have a local minimum or maximum at each \( x_i \).

   Therefore, \( P(X) \) will have:
   - A local minimum at \( x_1 \)
   - A local maximum at \( x_2 \)
   - A local minimum at \( x_3 \)

   This implies that \( P(X) \) will change direction at each of these points, creating intervals where \( P(X) \) is increasing or decreasing. Consequently, there will be at least one value \( C \) such that the equation \( P(x) = C \) has 4 distinct real roots. 

   Thus, \( P_4 \) is true.

2. **Case \( n = 5 \):**
   - Consider a polynomial \( P(X) \) of degree 5 with real coefficients.
   - Its derivative \( P'(X) \) is a polynomial of degree 4.
   - Given that \( P'(X) \) has 4 distinct real roots, say \( x_1 < x_2 < x_3 < x_4 \).

   Since \( P'(X) \) changes sign at each of these roots, \( P(X) \) will have local extrema at \( x_1, x_2, x_3, \) and \( x_4 \). Specifically:
   - \( P(X) \) will have a local maximum or minimum at each \( x_i \).

   Therefore, \( P(X) \) will have:
   - A local maximum at \( x_1 \)
   - A local minimum at \( x_2 \)
   - A local maximum at \( x_3 \)
   - A local minimum at \( x_4 \)

   This implies that \( P(X) \) will change direction at each of these points, creating intervals where \( P(X) \) is increasing or decreasing. Consequently, there will be at least one value \( C \) such that the equation \( P(x) = C \) has 5 distinct real roots. 

   Thus, \( P_5 \) is true.

The final answer is \( \boxed{ P_4 } \) and \( P_5 \) are both true.