1 + \Delta & -1\r
\end{pmatrix}\r
\begin{pmatrix}\r
- U_n\\ V_n\r
+ U_n\\\r
+ V_n\r
\end{pmatrix} &= \begin{pmatrix}\r
U_{n-1} + kg_1U_{n-1}^2 - kU_{n-1}^3\\\r
0\r
\end{aligned}$$\r
\r
As usual, we multiply each side of the equation by a\r
-test function $\overrightarrow\varphi_i = \begin{pmatrix}\r
+test function \r
+\r
+$$\overrightarrow\varphi_i = \begin{pmatrix}\r
\phi_i\\ \psi_i\r
-\end{pmatrix}$\r
+\end{pmatrix}$$\r
+\r
+to get the equation\r
\r
$$\begin{aligned}\r
\begin{pmatrix}\r
- \phi_i\\ \psi_i\r
+ \phi_i\\ \r
+ \psi_i\r
\end{pmatrix}\cdot\begin{pmatrix}\r
1 - kr & k(1 + \Delta)\\\r
1 + \Delta & -1\r
\begin{pmatrix}\r
U_n\\ V_n\r
\end{pmatrix} &= \begin{pmatrix}\r
- \phi_i\\\psi_i\r
+ \phi_i\\\r
+ \psi_i\r
\end{pmatrix}\cdot\begin{pmatrix}\r
U_{n-1} + kg_1U_{n-1}^2 - kU_{n-1}^3\\\r
0\r
\r
$$\begin{aligned}\r
\sum_j u_j\begin{pmatrix}\r
- \phi_i\\\psi_i\r
+ \phi_i\\\r
+ \psi_i\r
\end{pmatrix}\cdot\begin{pmatrix}\r
1 - kr & k(1 + \Delta)\\\r
1 + \Delta & -1\r
\begin{pmatrix}\r
\phi_j\\\psi_j\r
\end{pmatrix} &= \begin{pmatrix}\r
- \phi_i\\\psi_i\r
+ \phi_i\\\r
+ \psi_i\r
\end{pmatrix}\cdot\begin{pmatrix}\r
U_{n-1} + kg_1U_{n-1}^2 - kU_{n-1}^3\\\r
0\r