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Question 10

Let $$z$$ be a complex number such that $$|z| = 1$$. If $$\frac{2 + k^2 z}{k + \bar{z}} = kz$$, $$k \in \mathbb{R}$$, then the maximum distance of $$k + ik^2$$ from the circle $$|z - (1 + 2i)| = 1$$ is:

We are given $$|z| = 1$$ and $$\frac{2 + k^2z}{k + \bar{z}} = kz$$ where $$k \in \mathbb{R}$$.

Since $$|z| = 1$$, we have $$z\bar{z} = 1$$, so $$\bar{z} = \frac{1}{z}$$.

Substituting: $$\frac{2 + k^2z}{k + \frac{1}{z}} = kz$$.

Multiplying numerator and denominator of the left side by $$z$$: $$\frac{z(2 + k^2z)}{kz + 1} = kz$$.

$$\frac{2z + k^2z^2}{kz + 1} = kz$$

$$2z + k^2z^2 = kz(kz + 1) = k^2z^2 + kz$$

$$2z = kz$$

Since $$z \neq 0$$ (as $$|z| = 1$$), we get $$k = 2$$.

So the point $$k + ik^2 = 2 + 4i$$.

The circle is $$|z - (1 + 2i)| = 1$$ with center $$(1, 2)$$ and radius 1.

The distance from $$(2, 4)$$ to the center $$(1, 2)$$ is $$\sqrt{(2-1)^2 + (4-2)^2} = \sqrt{1 + 4} = \sqrt{5}$$.

The maximum distance from the point to the circle is $$\sqrt{5} + 1$$ (distance to center plus radius).

Hence, the correct answer is Option A.

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