- A0
- B1
- C2
- D3
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Correct answer: C
Let .
We interpret the two loci in the Argand plane.
- First locus:
This is a circle with center and radius .
So its equation is
- Second locus:
Here,
- is distance from ,
- is distance from .
Hence this is an ellipse with foci and , and sum of distances equal to .
Since for an ellipse, and distance between foci is , so Thus,
The center is , so the ellipse is
- Solve simultaneously
We need intersections of
and
Instead of solving fully algebraically, use geometry first.
The circle center is with radius . The ellipse is symmetric about the -axis.
Check whether the circle can meet the lower half of the ellipse:
- On the circle, lowest point is at .
- So any intersection must have . Thus only upper branch of ellipse matters.
Now parametrize the circle:
Substitute into ellipse:
This is cumbersome, so let us instead compare positions.
- Use upper branch of ellipse
From ellipse:
From circle (lower branch gives , upper branch gives larger values, but circle itself lies between and ):
Since ellipse upper branch has , intersections with the circle occur where
or
Geometrically, the ellipse's top is at , while the circle center is above and right of this. The circle spans .
Let us test key points:
- At , circle gives
Ellipse gives
No intersection.
- At , circle gives
Ellipse gives
So at , ellipse point lies between the two circle points, suggesting crossing.
Now compare functions on interval and .
Define
Intersections correspond to .
Compute signs:
- At :
- At :
So there is at least one root in .
- At , ellipse gives
Then
Since and , there is at least one root in .
Thus there are at least intersections.
Because the upper branch of the ellipse is single-valued and the circle arc over can cross it at most twice here, total intersections are exactly .
Therefore, the number of points of intersection is
So the correct option is C.
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