Ploting Polygon in Maple with more then 3 Dimensions

Question

I have a set of constraints with the variables $x_1$ and $x_2$. relations $= [-1 <= x_1, x_1 <= 1, -1/2 <= x_2, x_2 <= 3/2]$ and plotting the polygon works just fine in Maple when I use Plot(PolyhedralSet(relations)) but now I want to plot $x_3$ and $x_4$ depending on $x_1$ and $x_2$ like this relations$_2 = [x_3 = x_1 + x_2, x_4 = x_1 - x_2]$. The Problem is, that Maple can't plot this, because this isn't 3 dimensional anymore. I haven't found anything on how I can disregard plotting $x_1$ and $x_2$.

Answer 1

with(PolyhedralSets):
R := [-1<=x1, x1<=1, -1/2<=x2, x2<=3/2]:
C := [x3=x1+x2, x4=x1-x2]:

Rnew := eval(R,solve(C,[x1,x2])[1]);

   [-1 <= 1/2*x3+1/2*x4, 1/2*x3+1/2*x4 <= 1, 
    -1/2 <= -1/2*x4+1/2*x3, -1/2*x4+1/2*x3 <= 3/2]

Plot(PolyhedralSet(R));

Plot(PolyhedralSet(Rnew));