x     = (-128:128)'/128; 
A     = [x.^0 x.^1 x.^2 x.^3]; 
[Q,R] = qr(A,0); 
scale = Q(257,:); 
Q     = Q*diag(1 ./scale); 
%plot(Q)

hold on

aux1 = 1.5*x.^2 - 0.5;
aux2 = 2.5*x.^3 - 1.5*x;
B    = [x.^0 x.^1 aux1 aux2];
%plot(x,B)

aux1 = 2*x.^2 - 1;
aux2 = 4*x.^3 - 3*x;
C    = [x.^0 x.^1 aux1 aux2];
plot(x,C)