If the center of the dilation is the origin, then it is easy to calculate the coordinates of the figure after the dilation: just multiply the coordinates by the scale factor. I also show an example where the center of the dilation is one of the vertices of a triangle. Lastly, I present a question about the scale factor and the center of a certain dilation.
Basics of dilations — video lesson
Practice geometric transformations online
Math Mammoth Grade 8 curriculum