[Tex/LaTex] “Undefined control sequence. [\end{flalign*}]” error I can’t seem to fix

alignerrors

I actually get the error twice on the same line. Can't figure out what's causing it. My code:

\documentclass{article}
\usepackage[left=1in, top=1in, bottom=1in]{geometry}
\usepackage{amsmath}
\usepackage{amssymb}
\begin{document}

\begin{flalign*}
\textbf{14c)} \quad & \text{Let } V(x,y) \text{ be "} x \text{ has visited } y \text{",} &\\
                    & \text{where } x \in \{ \text{students in this class} \} \text{ and } y \in \{ \text{places} \} &\\
                    & \exists x (V(x, \text{Alaska}) \land \neg V(x, \text{Hawaii})) &\\
\textbf{d)}   \quad & \text{Let } L(x,y) \text{ be "} x \text{ has learned at least } y \text{ programming languages",} &\\
                    & \text{where } x \in \{ \text{students in this class} \} \text{ and } y \in \R &\\
                    & \forall x (L(x, 1)) &\\
\textbf{e)}   \quad & \text{Let } T(x,y) \text{ be "} x \text{ has taken every course offered by } y \text{",} &\\
                    & \text{where } x \in \{ \text{students in this class} \} \text{ and } y \in \{ \text{departments in this school} \} &\\
                    & \exists x,y (T(x,y))
\end{flalign*}
\end{document}

The error:
2.tex:80: Undefined control sequence. [\end{flalign*}]

Best Answer

It is probably what you needed (\R is now defined as blackboard R):

\documentclass{article}
\usepackage[left=1in, top=1in, bottom=1in]{geometry}
\usepackage{amsmath}
\usepackage{amssymb}

\newcommand\R{\mathbb{R}}

\begin{document}


\begin{flalign*}
\textbf{14c)} \quad & \text{Let } V(x,y) \text{ be "} x \text{ has visited } y \text{",} &\\
                    & \text{where } x \in \{ \text{students in this class} \} \text{ and } y \in \{ \text{places} \} &\\
                    & \exists x (V(x, \text{Alaska}) \land \neg V(x, \text{Hawaii})) &\\
\textbf{d)}   \quad & \text{Let } L(x,y) \text{ be "} x \text{ has learned at least } y \text{ programming languages",} &\\
                    & \text{where } x \in \{ \text{students in this class} \} \text{ and } y \in \R &\\
                    & \forall x (L(x, 1)) &\\
\textbf{e)}   \quad & \text{Let } T(x,y) \text{ be "} x \text{ has taken every course offered by } y \text{",} &\\
                    & \text{where } x \in \{ \text{students in this class} \} \text{ and } y \in \{ \text{departments in this school} \} &\\
                    & \exists x,y (T(x,y))
\end{flalign*}
\end{document}
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