# Locus Difference of Distances (Vertical)

What is the locus of points for which the difference of the distances to F1 and F2 is 6?
1. Use the POINT tool to plot as many points as you can in this locus.
Use the ARROW tool to click SHOW DISTANCES to see distances to F1 and F2 from points in the locus.
2. Use the ARROW tool to click SHOW ME to see all of the points in this locus.
Notice the equation for this locus. How is it different from the equation of an ellipse or circle?
3. Drag F2 to see how the locus changes when the foci are closer together or further apart.
4. Try changing the difference from 6 to another number.
Are there differences you can't use for these foci? What if you move the foci?

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