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Let the eccentricity of an ellipse $$\frac{x^2}{a^2} + \frac{y^2}{b^2} = 1, a > b$$, be $$\frac{1}{4}$$. If this ellipse passes through the point $$\left(-4\sqrt{\frac{2}{5}}, 3\right)$$, then $$a^2 + b^2$$ is equal to
We are given an ellipse $$\frac{x^2}{a^2} + \frac{y^2}{b^2} = 1$$ with $$a > b$$ and eccentricity $$e = \frac{1}{4}$$. For such an ellipse, the eccentricity satisfies
$$e^2 = 1 - \frac{b^2}{a^2}$$
so
$$\frac{1}{16} = 1 - \frac{b^2}{a^2},$$
which implies
$$\frac{b^2}{a^2} = 1 - \frac{1}{16} = \frac{15}{16},$$
and hence
$$b^2 = \frac{15a^2}{16}.$$
The ellipse also passes through the point $$\left(-4\sqrt{\frac{2}{5}},\;3\right)$$. Substituting this into the equation of the ellipse gives
$$\frac{\left(-4\sqrt{\frac{2}{5}}\right)^2}{a^2} + \frac{3^2}{b^2} = 1,$$
which simplifies to
$$\frac{16 \times \frac{2}{5}}{a^2} + \frac{9}{b^2} = 1$$
and therefore
$$\frac{32}{5a^2} + \frac{9}{b^2} = 1.$$
Next, substituting $$b^2 = \frac{15a^2}{16}$$ into this equation yields
$$\frac{32}{5a^2} + \frac{9 \times 16}{15a^2} = 1,$$
or
$$\frac{32}{5a^2} + \frac{144}{15a^2} = 1.$$
Since $$\frac{144}{15} = \frac{48}{5},$$ this becomes
$$\frac{32}{5a^2} + \frac{48}{5a^2} = 1,$$
so
$$\frac{80}{5a^2} = 1 \quad\Longrightarrow\quad \frac{16}{a^2} = 1 \quad\Longrightarrow\quad a^2 = 16.$$
Substituting back to find $$b^2$$ gives
$$b^2 = \frac{15 \times 16}{16} = 15.$$
Finally,
$$a^2 + b^2 = 16 + 15 = 31.$$
The correct answer is Option B: $$31$$.
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