A dilation is a transformation
![D_{o,\, k}](https://tex.z-dn.net/?f=D_%7Bo%2C%5C%2C%20k%7D)
, with center O and a scale factor of k that is not zero, that maps O to itself and any other point P to P'.
The center O is a fixed point, P' is the image of P, points O, P and P' are on the same line.
In a dilation of
![D_{o,\, k}](https://tex.z-dn.net/?f=D_%7Bo%2C%5C%2C%20k%7D)
the scale factor, k is mapping the original figure to the image in such a way that the
distances from O to the vertices of the image are k times the distances
from O to the original figure. Also the size of the image are k times the
size of the original figure.
Thus for a dilation using the rule
![D_{o,\ k}=(5,\, 0)\rightarrow (10,\, 0)](https://tex.z-dn.net/?f=D_%7Bo%2C%5C%20k%7D%3D%285%2C%5C%2C%200%29%5Crightarrow%20%2810%2C%5C%2C%200%29)
results in the distance of the image form O being twice the distance of the original point from O.
Therefore, it can be observed that the scale factor of the dilation, k, is 2.