How do you convert this equation into Latex? I tried to do it and it gave me "undefined control sequence"

Question

How do you convert this equation into Latex? I tried to do it and it gave me "undefined control sequence"..

The equation I want to produce in my pdflatex:

My solution:

$Ker(f) = \{\alpha(0, 1, -1), \alpha \in \R \}$ 

Error:

Undefined control sequence

Answer 1

\R is not a macro which is defined by default. If you would like to use it, you can for example define it like this:

\documentclass{article}

\usepackage{amsmath}
\usepackage{amsfonts}
\newcommand{\R}{\mathbb{R}}

\begin{document}

$\text{Ker}(f) = \{\alpha(0, 1, -1), \alpha \in \R \}$ 

\end{document}