\[
\boxed{
 \left( ay \left( x \right) -bx \right) ^{2} \left( {a}^{2} \left( {\frac {\rm d}{{\rm d}x}}y \left( x \right)  \right) ^{2}+{b}^{2} \right) -{c}^{2} \left( a{\frac {\rm d}{{\rm d}x}}y \left( x \right) +b \right) ^{2}=0}
\]