lie-algebras-and-their-representations

diff --git a/sections/introduction.tex b/sections/introduction.tex
@@ -917,8 +917,8 @@ define\dots
 \begin{example}\label{ex:sl2-polynomial-subrep}
   Let \(K[x, y]\) be the \(\mathfrak{sl}_2(K)\)-module as in
   example~\ref{ex:sl2-polynomial-rep}. Since \(e\), \(f\) and \(h\) all
-  preserve the degree of monomials, the space \(K[x, y]^{(n)} = \bigoplus_{k = 0}^n
-  K x^{n - k} y^k\) of homogeneous polynomials of degree \(n\) is a
+  preserve the degree of monomials, the space \(K[x, y]^{(n)} = \bigoplus_{k +
+  \ell = n} K x^k y^\ell\) of homogeneous polynomials of degree \(n\) is a
   finite-dimensional subrepresentation of \(K[x, y]\).
 \end{example}