Consider the curve given by the equation

$\backslash [$xy$^2+5$xy$=50\backslash ].$ It can be shown that

$\backslash [\backslash$dfrac$\{$dy$\}\{$dx$\}=\backslash$dfrac$\{-$y$($y$+5)\}\{$x$(2$y$+5)\}\backslash ].$

Write the equation of the vertical line that is tangent to the curve.