First find the coordinates of the vertex B. The center of the square M is the midpoint of the diagonal AC. Since A(2,7) and C(8,1), the center has coordinates
Point M is also the midpoint of the diagonal BD. Let B has coordinates (x,y), then
Hence, B(8,7).
Now, the dilation by a scale factor 2 with the center of dilation at the origin has the rule