You have an improper &
in the last line of the second alignment, which sets up a second set of alignments; those columns are empty, but the space between the first and the second set is accounted for.
You also have trailing \\
that should be removed.
Original
\documentclass{article}
\usepackage{amsmath}
\usepackage{showframe} % just for the example
\begin{document}
words
\begin{align*}
1&=ak_1+bl_1\\
n&=n(ak_1+bl_1)\\
&=nak_1+nbl_1\\
&=ak_n+bl_n\\
\end{align*}
words
\begin{align*}
n&=ak_n+bl_n\\
&=ak_n+abx+bl_n-abx\\
&=a(k_n+bx)+b(l_n-ax)\\
&=ar+bs&\\
\end{align*}
more words
\end{document}

Fixed version
\documentclass{article}
\usepackage{amsmath}
\usepackage{showframe} % just for the example
\begin{document}
words
\begin{align*}
1&=ak_1+bl_1\\
n&=n(ak_1+bl_1)\\
&=nak_1+nbl_1\\
&=ak_n+bl_n
\end{align*}
words
\begin{align*}
n&=ak_n+bl_n\\
&=ak_n+abx+bl_n-abx\\
&=a(k_n+bx)+b(l_n-ax)\\
&=ar+bs
\end{align*}
more words
\end{document}

Note
The frame is just for demonstration purposes. Don't load the showframe
package yourself.
&\\
in the second alignment: remove it.\documentclass{...}
, the required\usepackage
's,\begin{document}
, and\end{document}
. That may seem tedious to you, but think of the extra work it represents for TeX.SX users willing to give you a hand. Help them help you: remove that one hurdle between you and a solution to your problem.&
in the final line of the secondalign*
environment supposed to achieve?