1. **State the problem:** Write the quadratic equation $y = -x^2 - 4x + 5$ in vertex form, identify the axis of symmetry, extrema, and zeros.
2. **Recall vertex form:** The vertex form of a quadratic is $$y = a(x - h)^2 + k$$ where $(h, k)$ is the vertex.
3. **Complete the square:** Start with $$y = -x^2 - 4x + 5$$
Factor out the coefficient of $x^2$ from the first two terms:
$$y = -\left(x^2 + 4x\right) + 5$$
4. To complete the square inside the parentheses, take half of 4, which is 2, and square it: $2^2 = 4$.
Add and subtract 4 inside the parentheses:
$$y = -\left(x^2 + 4x + 4 - 4\right) + 5$$
Rewrite:
$$y = -\left((x + 2)^2 - 4\right) + 5$$
Distribute the negative sign:
$$y = - (x + 2)^2 + 4 + 5$$
Simplify:
$$y = - (x + 2)^2 + 9$$
5. **Vertex form:** $$y = -1(x - (-2))^2 + 9$$
6. **Axis of symmetry:** The axis of symmetry is the vertical line through the vertex $x = -2$.
7. **Extrema:** Since $a = -1 < 0$, the parabola opens downward, so the vertex is a maximum point at $(-2, 9)$.
8. **Find zeros:** Set $y=0$:
$$0 = - (x + 2)^2 + 9$$
Rearranged:
$$(x + 2)^2 = 9$$
Take square root:
$$x + 2 = \pm 3$$
Solve for $x$:
$$x = -2 + 3 = 1$$
$$x = -2 - 3 = -5$$
Zeros are at $(-5, 0)$ and $(1, 0)$, listed from least to greatest.
**Final answers:**
- Vertex form: $$y = -1(x - (-2))^2 + 9$$
- Axis of symmetry: $$x = -2$$
- Extrema: maximum at $$(-2, 9)$$
- Zeros: $$(-5, 0)$$ and $$(1, 0)$$
Vertex Form B3Fa10
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