Consider the dilation equation (9.138) with $c_0=0, c_1=c_2=1$, so $\varphi(x)=$ $\varphi(2 x-1)+\varphi(2 x-2)$. Prove that $\psi(x)=\varphi(x+1)$ satisfies the Haar dilation equation (9.139). Generalize this result to prove that we can always, without loss of generality, assume that $c_0 \neq 0$ in the general dilation equation (9.138).