One-dimensional scaling (also called a strain, or in GeoGebra a stretch) is a transformation that stretches in one direction by a certain amount. The stretching goes outwards from a specified line, called the center or axis. There is a scale factor S that determines the amount of scaling. Each point being scaled moves at right angles to the center line, and moves to a point S times as far from the line.
Drag the ScaleFactor slider and move the center line EF to change the scaling transformation.
Drag blue points to change the shapes and sizes of the objects being scaled.

This transformation uses the command Stretch[a,b,S] typed on the Input line, where a is the object being scaled, b is the center line, and S is the scale factor.