1. **State the problem:** Find the possible rational zeros of the polynomial $$f(x) = x^4 + 4x^3 - x^2 - 16x - 12$$ and test them to find actual zeros.
2. **Use the Rational Root Theorem:** Possible rational zeros are of the form $$\pm \frac{p}{q}$$ where $p$ divides the constant term and $q$ divides the leading coefficient.
3. **Identify factors:**
- Leading coefficient is 1, factors: $\pm 1$
- Constant term is $-12$, factors: $\pm 1, \pm 2, \pm 3, \pm 4, \pm 6, \pm 12$
4. **Possible rational zeros:**
$$\pm 1, \pm 2, \pm 3, \pm 4, \pm 6, \pm 12$$
5. **Test zeros by substitution or synthetic division:**
- Test $x=1$: $1 + 4 - 1 - 16 - 12 = -24 \neq 0$
- Test $x=-1$: $1 - 4 - 1 + 16 - 12 = 0$ (zero found)
6. **Divide polynomial by $(x+1)$:**
$$\frac{x^4 + 4x^3 - x^2 - 16x - 12}{x+1} = x^3 + 3x^2 - 4x - 12$$
7. **Repeat Rational Root Theorem on quotient:**
Possible zeros: same as before.
8. **Test $x=2$:**
$$2^3 + 3(2)^2 - 4(2) - 12 = 8 + 12 - 8 - 12 = 0$$ (zero found)
9. **Divide quotient by $(x-2)$:**
$$\frac{x^3 + 3x^2 - 4x - 12}{x-2} = x^2 + 5x + 6$$
10. **Factor quadratic:**
$$x^2 + 5x + 6 = (x+2)(x+3)$$
11. **Final factorization:**
$$f(x) = (x+1)(x-2)(x+2)(x+3)$$
12. **Zeros:**
$$x = -1, 2, -2, -3$$
**Answer:** The rational zeros of $f(x)$ are $-3, -2, -1,$ and $2$.
Rational Zeros 954A6C
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