Ratio Point-Line
This activity belongs to the GeoGebra book GeoGebra Principia.
When the quotient of the distances of the points of the sought-after locus to point A and line r is a constant k, we obtain a conic section, which will be an ellipse, parabola or hyperbola depending on whether the value of k (eccentricity) is less than 1, equal to 1, or greater than 1, respectively 
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- Note: For a better view of the construction, it is recommended to download the ggb file here.
Author of the construction of GeoGebra: Rafael Losada.