%% There is only one extremal NS of type [-1,x2,1] (the CNS).
%%
%% polys
%%
   4x^2+(-4x2+4)x+(-5 x2+1)
   4x^2+(-4x2-4)x+(5 x2+1)
%%
%% input formula QEPCAD
%% 
   (Ax)[[-1<x2 /\ x2<1]/\[[-1<=x /\ x<x2] ==> 4x^2+(-4 x2+4)x+(-5 x2+1)>=0] /\ [[x2<x /\ x<=1] ==> 4x^2+(-4x2-4)x+(5 x2+1)>=0]].
%%
%% input formula MMA
%%
   -1<x2<1\[And]ForAll[x,(-1<=x<x2\[Implies]4x^2+(-4x2+4)x+(-5 x2+1)>=0)\[And](x2<x<=1\[Implies]4x^2+(-4x2-4)x+(5 x2+1)>=0)]