\[
\boxed{
{\frac {\rm d}{{\rm d}x}}y \left( x \right) -f \left( x \right)  \left( y \left( x \right) -g \left( x \right)  \right) \sqrt { \left( y \left( x \right) -a \right)  \left( y \left( x \right) -b \right) }=0}
\]