1. **State the problem:** We need to create a sign chart for the function $$g(x) = -x^4 + 2x^3 + 8x^2$$ to determine where the function is positive, negative, or zero.
2. **Find the roots of the function:** Set $$g(x) = 0$$ and solve for $$x$$.
$$-x^4 + 2x^3 + 8x^2 = 0$$
3. **Factor the expression:**
$$-x^2(x^2 - 2x - 8) = 0$$
4. **Solve each factor:**
- From $$-x^2 = 0$$, we get $$x = 0$$.
- From $$x^2 - 2x - 8 = 0$$, use the quadratic formula:
$$x = \frac{2 \pm \sqrt{(-2)^2 - 4 \cdot 1 \cdot (-8)}}{2 \cdot 1} = \frac{2 \pm \sqrt{4 + 32}}{2} = \frac{2 \pm \sqrt{36}}{2} = \frac{2 \pm 6}{2}$$
So,
$$x = \frac{2 + 6}{2} = 4$$ and $$x = \frac{2 - 6}{2} = -2$$.
5. **Roots are:** $$x = -2, 0, 4$$.
6. **Determine the sign of $$g(x)$$ in intervals divided by the roots:**
Intervals: $$(-\infty, -2), (-2, 0), (0, 4), (4, \infty)$$.
7. **Test points in each interval:**
- For $$x = -3$$ in $$(-\infty, -2)$$:
$$g(-3) = -(-3)^4 + 2(-3)^3 + 8(-3)^2 = -81 - 54 + 72 = -63 < 0$$
- For $$x = -1$$ in $$(-2, 0)$$:
$$g(-1) = -1 + (-2) + 8 = 5 > 0$$
- For $$x = 1$$ in $$(0, 4)$$:
$$g(1) = -1 + 2 + 8 = 9 > 0$$
- For $$x = 5$$ in $$(4, \infty)$$:
$$g(5) = -625 + 250 + 200 = -175 < 0$$
8. **Sign chart summary:**
- $$g(x) < 0$$ on $$(-\infty, -2) \cup (4, \infty)$$
- $$g(x) > 0$$ on $$(-2, 0) \cup (0, 4)$$
- $$g(x) = 0$$ at $$x = -2, 0, 4$$
**Final answer:**
$$g(x)$$ is negative for $$x < -2$$ and $$x > 4$$, positive between $$-2$$ and $$4$$ except at $$0$$ where it is zero.
Sign Chart 86B3Ae
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