Answer
$\dfrac{y}{x-y}$
Work Step by Step
The given expression, $
\dfrac{1+\dfrac{x}{y}}{\dfrac{x^2}{y^2}-1}
,$ simplifies to
\begin{array}{l}\require{cancel}
\dfrac{\dfrac{y+x}{y}}{\dfrac{x^2-y^2}{y^2}}
\\\\=
\dfrac{y+x}{y}\div\dfrac{x^2-y^2}{y^2}
\\\\=
\dfrac{y+x}{y}\cdot\dfrac{y^2}{x^2-y^2}
\\\\=
\dfrac{x+y}{y}\cdot\dfrac{y^2}{(x+y)(x-y)}
\\\\=
\dfrac{\cancel{x+y}}{\cancel{y}}\cdot\dfrac{\cancel{y}\cdot y}{(\cancel{x+y})(x-y)}
\\\\=
\dfrac{y}{x-y}
.\end{array}