in general if you have a point P that you are going to scale about a center of dilation (cx,cy) you end up with
$$P'=sf((P_x-c_x), (P_y-c_y))+(c_x,c_y)=$$
$$(sf(P_x-c_x)+c_x,~sf(P_y-c_y)+c_y)$$
here
$$c_x=c_y=0,~~sf=0.5$$
so we end up with
$$P'=(0.5 P_x, 0.5 P_y)$$
applying that to P=(2,2) we get
$$P'=(0.5\cdot 2, 0.5 \cdot 2)=(1,1)$$
you can figure out the rest of them