Homothety
A homothety h with center O maps X to X ′ . Construct the homotheties of Y and m.
A homothety with center O and factor k > 0 maps a point X to a point X' on [OX) such that OX' = k · OX.
For k < 0, the point X' is defined as the point on (OX) \ [OX) such that OX' = |k| · OX.