1. **State the problem:** We are given the quadratic equation $$x^2 - 2x - 9 = 0$$ and told one solution can be written as $$1 + \sqrt{k}$$. We need to find the value of $$k$$.
2. **Recall the quadratic formula:** For an equation $$ax^2 + bx + c = 0$$, the solutions are given by
$$x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}$$
3. **Identify coefficients:** Here, $$a=1$$, $$b=-2$$, and $$c=-9$$.
4. **Calculate the discriminant:**
$$b^2 - 4ac = (-2)^2 - 4(1)(-9) = 4 + 36 = 40$$
5. **Find the roots using the quadratic formula:**
$$x = \frac{-(-2) \pm \sqrt{40}}{2(1)} = \frac{2 \pm \sqrt{40}}{2} = 1 \pm \frac{\sqrt{40}}{2}$$
6. **Rewrite the root in the form $$1 + \sqrt{k}$$:**
We want to express $$1 + \frac{\sqrt{40}}{2}$$ as $$1 + \sqrt{k}$$.
7. **Equate and solve for $$k$$:**
$$\sqrt{k} = \frac{\sqrt{40}}{2} = \sqrt{\frac{40}{4}} = \sqrt{10}$$
Thus, $$k = 10$$.
**Final answer:** $$k = 10$$ (Option B).
Quadratic Root
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