\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{align*}
y(x)
={}& \frac{
\sqrt {a} \bigl(
\sin ( 0{,}2\,\sqrt {a}\sqrt {x} ) C_{1} + \cos ( 0{,}2\,\sqrt {a}\sqrt {x} )
\bigr)
}{
\sqrt {x} \bigl(
\sin ( 1{,}2\,\sqrt {a}\sqrt {x} ) C_{1} + \cos ( 1{,}2\,\sqrt {a}\sqrt {x} )
\bigr)
} \\
{}\cdot{}& \frac{
\sqrt {a} \bigl(
\sin ( 0{,}2\,\sqrt {a}\sqrt {x} ) C_{1} + \cos ( 0{,}2\,\sqrt {a}\sqrt {x} )