1. **State the problem:** We want to express the quadratic expression $$q + 12x - qx^2$$ in the form $$a - b(x - c)^2$$ where $$a$$, $$b$$, and $$c$$ are expressed in terms of $$q$$.
2. **Recall the formula:** The expression $$a - b(x - c)^2$$ represents a quadratic in vertex form, where $$a$$ is the maximum value, $$b$$ is the coefficient controlling the width and direction, and $$c$$ is the x-coordinate of the vertex.
3. **Rewrite the original expression:**
$$q + 12x - qx^2 = -qx^2 + 12x + q$$
4. **Complete the square:**
Start by factoring out $$-q$$ from the terms involving $$x$$:
$$-q(x^2 - \frac{12}{q}x) + q$$
5. **Complete the square inside the parentheses:**
Take half the coefficient of $$x$$ inside the parentheses:
$$\frac{12}{q} \times \frac{1}{2} = \frac{6}{q}$$
Square it:
$$\left(\frac{6}{q}\right)^2 = \frac{36}{q^2}$$
Add and subtract this inside the parentheses:
$$-q\left(x^2 - \frac{12}{q}x + \frac{36}{q^2} - \frac{36}{q^2}\right) + q$$
Rewrite as:
$$-q\left(\left(x - \frac{6}{q}\right)^2 - \frac{36}{q^2}\right) + q$$
6. **Distribute $$-q$$:**
$$-q\left(x - \frac{6}{q}\right)^2 + q \times \frac{36}{q^2} + q = -q\left(x - \frac{6}{q}\right)^2 + \frac{36}{q} + q$$
7. **Combine constants:**
$$a = q + \frac{36}{q}$$
$$b = q$$
$$c = \frac{6}{q}$$
8. **Final expression:**
$$q + 12x - qx^2 = a - b(x - c)^2 = \left(q + \frac{36}{q}\right) - q\left(x - \frac{6}{q}\right)^2$$
**Answer:**
$$a = q + \frac{36}{q}, \quad b = q, \quad c = \frac{6}{q}$$
Quadratic Completion 806F69
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