Find the value of `a` and `b` so that the polynomial `x^3-a x^2-13 x+b` has `(x-1)` and `(x+3)` as factors.

Explanation

To find the values of \( a \) and \( b \) such that the polynomial \( P(x) = x^3 - ax^2 - 13x + b \) has \( (x-1) \) and \( (x+3) \) as factors, we can use the fact that if \( (x-c) \) is a factor of \( P(x) \), then \( P(c) = 0 \).

### Step 1: Set up the polynomial
The polynomial is given as:
\[ P(x) = x^3 - ax^2 - 13x + b \]

...