1. **State the problem:**
We have the quadratic equation $$k + 9 = (6 - x)(2x + 1)$$ and need to find:
(a) The range of values of $$k$$ for which the equation has two distinct real roots.
(b) For the largest integer $$k$$ in that range, solve the quadratic equation.
2. **Expand and rearrange the equation:**
Expand the right side:
$$(6 - x)(2x + 1) = 6 \times 2x + 6 \times 1 - x \times 2x - x \times 1 = 12x + 6 - 2x^2 - x = -2x^2 + 11x + 6$$
So the equation becomes:
$$k + 9 = -2x^2 + 11x + 6$$
Rearranged to standard quadratic form:
$$-2x^2 + 11x + 6 - (k + 9) = 0$$
$$-2x^2 + 11x + 6 - k - 9 = 0$$
$$-2x^2 + 11x - (k + 3) = 0$$
3. **Rewrite the quadratic equation:**
$$-2x^2 + 11x - (k + 3) = 0$$
Multiply both sides by $$-1$$ to simplify:
$$2x^2 - 11x + (k + 3) = 0$$
4. **Condition for two distinct real roots:**
For a quadratic $$ax^2 + bx + c = 0$$ to have two distinct real roots, the discriminant $$\Delta$$ must be positive:
$$\Delta = b^2 - 4ac > 0$$
Here, $$a = 2$$, $$b = -11$$, $$c = k + 3$$.
Calculate discriminant:
$$\Delta = (-11)^2 - 4 \times 2 \times (k + 3) = 121 - 8(k + 3)$$
5. **Find range of $$k$$:**
Set $$\Delta > 0$$:
$$121 - 8(k + 3) > 0$$
$$121 - 8k - 24 > 0$$
$$97 - 8k > 0$$
$$-8k > -97$$
Divide both sides by $$-8$$, reversing inequality:
$$\cancel{-8}k > \cancel{-97}$$
$$\cancel{-8}k > \cancel{-97}$$
$$k < \frac{97}{8}$$
So the range of $$k$$ for two distinct real roots is:
$$k < 12.125$$
6. **Find the largest integer $$k$$:**
The largest integer less than $$12.125$$ is $$12$$.
7. **Solve the quadratic for $$k = 12$$:**
Substitute $$k = 12$$ into the quadratic:
$$2x^2 - 11x + (12 + 3) = 0$$
$$2x^2 - 11x + 15 = 0$$
Calculate discriminant:
$$\Delta = (-11)^2 - 4 \times 2 \times 15 = 121 - 120 = 1$$
Use quadratic formula:
$$x = \frac{-b \pm \sqrt{\Delta}}{2a} = \frac{11 \pm 1}{4}$$
Calculate roots:
$$x_1 = \frac{11 + 1}{4} = \frac{12}{4} = 3$$
$$x_2 = \frac{11 - 1}{4} = \frac{10}{4} = 2.5$$
**Final answers:**
(a) The range of $$k$$ is $$k < 12.125$$.
(b) For $$k = 12$$, the roots are $$x = 3$$ and $$x = 2.5$$.
Quadratic K Values Af0325
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