# Missing $inserted error in Latex using matrix in the following latex code:  $\begin{bmatrix} d_1 & e_1 & 0 & \cdots & 0\\ c_1 & d_2 & e_2 & \ddots & \vdots \\ 0 & \ddots & \ddots & \ddots & 0 \\ \vdots & \ddots & \ddots & \ddots & e_N\\ 0 & \cdots & 0 & 0 & c_N & d_N \end{bmatrix}$ where$c_i = -1-\frac{h}{2}p(x_i),d_i = 2+h^2q(x_i)\;$and\;$e_i=-1-\frac{h}{2}p(x_i)$\\ $\textbf{b} = \begin{bmatrix} -h^{2}r(x_1)+(1+\frac{h}{2}p(x_1))y_0\\ -h^{2}r(x_2)\\ \vdots\\ -h^{2}r(x_{N-1})\\ -h^{2}r(x_N)+(1-\frac{h}{2}p(x_N))y_{N+1} \end{bmatrix}$  • Welcome to TeX. SE! (i) please always provide MWE (Minimal Working Example), a small but complete document, (ii(matrix had to be used inside math environment (iii) all $ inside matrix had to be removed, (iv) your problem has nothing with Overleaf. Apr 21, 2021 at 18:04

There are several errors in your code. Among the serious ones:

• $ and $ initiate and terminate an unnumbered displaymath environment. Don't use $ to initiate and terminate inline math mode when you're already in display math mode. Hence, you must remove all $ instances inside both bmatrix environments.

• $c_i = -1-\frac{h}{2}p(x_i),d_i = 2+h^2q(x_i)\;$ and\; $e_i=-1-\frac{h}{2}p(x_i)$ is wrong; it should be

$c_i = -1-\frac{h}{2}p(x_i)$, $d_i = 2+h^2q(x_i)$, and $e_i=-1-\frac{h}{2}p(x_i)$


i.e., you should use three separate inline math groups. Why? There are, syntactically speaking, three separate formulas on that line.

• The final row of the first bmatrix environment has a surplus 0 &.

• The instance of c_1 in row 2 should be c_2, and the instance of e_N in the second-to-last row should be e_{N-1}, right?

• Not an outright error, but an inaccuracy: Write \mathbf{b}, not \textbf{b}, while in math mode.

• To make the material look less cramped, I'd replace all four instances of \frac{h}{2} with it inline-math equivalent, (h/2).

\documentclass{article}
\usepackage{amsmath} % for 'bmatrix' environment
\begin{document}
$\begin{bmatrix} d_1 & e_1 & 0 & \cdots & 0 \\ c_2 & d_2 & e_2 & \ddots & \vdots \\ 0 & c_3 & \ddots & \ddots & 0 \\ \vdots & \ddots & \ddots & d_{N-1} & e_{N-1} \\ 0 & \cdots & 0 & c_N & d_N \end{bmatrix}$
where $c_i = -1-(h/2)p(x_i)$, $d_i = 2+h^2q(x_i)$, and $e_i=-1-(h/2)p(x_i)$.
$\mathbf{b} = \begin{bmatrix} -h^{2}r(x_1)+(1+(h/2)p(x_1))y_0 \\ -h^{2}r(x_2) \\ \vdots\\ -h^{2}r(x_{N-1}) \\ -h^{2}r(x_N)+(1-(h/2)p(x_N))y_{N+1} \end{bmatrix}$
\end{document}

• Thanks I understand all my mistakes Apr 22, 2021 at 4:51

I guessing that you like to achieve the following result:

\documentclass{beamer}
\usepackage[low-sup]{subdepth}

\begin{document}
\begin{frame}
$\begin{bmatrix} d_1 & e_1 & 0 & \cdots & 0 \\ c_1 & d_2 & e_2 & \ddots & \vdots \\ 0 & c_2 & \ddots & \ddots & 0 \\ \vdots & \ddots & \ddots & \d-{N-1} & e_{N-1} \\ 0 & \cdots & 0 & c_N & d_N \\ \end{bmatrix}$
where $c_i = -1-\frac{h}{2}p(x_i)$, $d_i = 2+h^2q(x_i)$ and $e_i=-1-\frac{h}{2}p(x_i)$
$\textbf{b} = \begin{bmatrix} -h^{2}r(x_1)+(1+\frac{h}{2}p(x_1))y_0\\ -h^{2}r(x_2)\\ \vdots\\ -h^{2}r(x_{N-1})\\ -h^{2}r(x_N)+(1-\frac{h}{2}p(x_N))y_{N+1} \end{bmatrix}$
\end{frame}
\end{document}
`