I'm given the maps $F_4(x)=4x(1-x)$ on $[0,1]$, $G(x)=4x^3-3x$ on $[-1,1]$ and $H(x)=8x^4-8x^2+1$ on $[-1,1]$. I managed to show that all these maps exhibit chaotic behavior and are conjugate to the tent maps $T_2,T_3,T_4$, respectively, where the tent maps are piecewise linear maps satisfying $T_2(0)=T_2(1)=0$, $T_2(\frac12)=1$, next $T_3(0)=T_3(\frac23)=0$, $T_3(\frac13)=T_3(1)=1$ and finally $T_4(0)=T_4(\frac12)=T_4(1)=0$, $T_4(\frac14)=T_4(\frac34)=1$.
I also showed that with $D_N(x)=Nx\mod1$, we have that $D_2$ is semi-conjugate to $F_4$, $D_3$ to $G$ and $D_4$ to $H$.
Now I'm asked to argue that none of the maps $F_4,G,H$ are structurally stable. How does one prove this? I believe that this would follow if I can show that the tent maps $T_k$ are not structurally stable, but I don't see how to prove this either, and I cannot find a reference.
The map $F_4$ seems a bit easier since we can just compare it to $F_{4+\epsilon}$ for some small $\epsilon>0$.
Any hint or help is much appreciated.