1. **State the problem:** Convert the quadratic function $f(x) = -2x^2 - 4x + 5$ from standard form to vertex form.
2. **Recall the vertex form:** The vertex form of a quadratic is $$f(x) = a(x-h)^2 + k$$ where $(h,k)$ is the vertex.
3. **Start with the given function:** $$f(x) = -2x^2 - 4x + 5$$
4. **Factor out the coefficient of $x^2$ from the first two terms:** $$f(x) = -2(x^2 + 2x) + 5$$
5. **Complete the square inside the parentheses:**
- Take half of the coefficient of $x$, which is 2, so half is 1.
- Square it: $1^2 = 1$.
- Add and subtract 1 inside the parentheses to complete the square:
$$f(x) = -2(x^2 + 2x + 1 - 1) + 5$$
6. **Rewrite the trinomial as a perfect square and simplify:**
$$f(x) = -2((x + 1)^2 - 1) + 5$$
7. **Distribute the $-2$ and simplify:**
$$f(x) = -2(x + 1)^2 + 2 + 5$$
$$f(x) = -2(x + 1)^2 + 7$$
8. **Final vertex form:** $$f(x) = -2(x + 1)^2 + 7$$
This shows the vertex is at $(-1, 7)$ and the parabola opens downward because $a = -2 < 0$.
Quadratic Vertex 637A23
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