\cfrac{AE}{h}      \begin{bmatrix}        1 & -1 & 0 & 0 \\       -1 & 2 & -1 & 0 \\       0 & -1 & 2 & -1 \\       0 & 0 & -1 & 2      \end{bmatrix}     \begin{bmatrix} u_1 \\ u_2 \\ u_3 \\ u_4 \end{bmatrix} =      \cfrac{a}{h}     \begin{bmatrix}       \left(\cfrac{x_2(x_2^2-x_1^2)}{2} - \cfrac{x_2^3-x_1^3}{3}\right) \\       \left(\cfrac{x_2^3-x_1^3}{3} - \cfrac{x_1(x_2^2-x_1^2)}{2}\right) +         \left(\cfrac{x_3(x_3^2-x_2^2)}{2} - \cfrac{x_3^3-x_2^3}{3}\right) \\       \left(\cfrac{x_3^3-x_2^3}{3} - \cfrac{x_2(x_3^2-x_2^2)}{2}\right) +         \left(\cfrac{x_4(x_4^2-x_3^2)}{2} - \cfrac{x_4^3-x_3^3}{3}\right) \\       \left(\cfrac{x_4^3-x_3^3}{3} - \cfrac{x_3(x_4^2-x_3^2)}{2}\right) +          \boldsymbol{R}\cfrac{h}{a}     \end{bmatrix}
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