\[
\boxed{
 \left\{ {\frac {\rm d}{{\rm d}t}}x \left( t \right) =x \left( t \right)  \left( a \left( px \left( t \right) +qy \left( t \right)  \right) +\alpha \right) ,{\frac {\rm d}{{\rm d}t}}y \left( t \right) =y \left( t \right)  \left( \beta+b \left( px \left( t \right) +qy \left( t \right)  \right)  \right)  \right\} }
\]