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The differential equation of the family of circles passing through the points (0, 2) and (0, -2) is
We need the differential equation of the family of circles passing through $$(0, 2)$$ and $$(0, -2)$$.
The general circle equation is $$x^2 + y^2 + 2gx + 2fy + c = 0$$. Substituting $$(0, 2)$$: $$4 + 4f + c = 0$$. Substituting $$(0, -2)$$: $$4 - 4f + c = 0$$.
Adding these two equations gives $$8 + 2c = 0$$, so $$c = -4$$. Subtracting gives $$8f = 0$$, so $$f = 0$$.
The family of circles is therefore $$x^2 + y^2 + 2gx - 4 = 0$$, with $$g$$ as the only parameter to be eliminated.
Differentiating with respect to $$x$$: $$2x + 2y\frac{dy}{dx} + 2g = 0$$, which gives $$g = -x - y\frac{dy}{dx}$$.
Substituting this back into the circle equation:
$$x^2 + y^2 + 2\left(-x - y\frac{dy}{dx}\right)x - 4 = 0$$
$$x^2 + y^2 - 2x^2 - 2xy\frac{dy}{dx} - 4 = 0$$
Simplifying: $$-x^2 + y^2 - 2xy\frac{dy}{dx} - 4 = 0$$. Multiplying through by $$-1$$:
$$2xy\frac{dy}{dx} + (x^2 - y^2 + 4) = 0$$
Hence, the correct answer is Option A.
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