\[
\boxed{
 \left\{ {\it a1}\,{\frac {{\rm d}^{2}}{{\rm d}{t}^{2}}}x \left( t \right) +{\it b1}\,{\frac {\rm d}{{\rm d}t}}x \left( t \right) +{\it c1}\,x \left( t \right) -A{\frac {\rm d}{{\rm d}t}}y \left( t \right) =B{{\rm e}^{i\omega\,t}},{\it a2}\,{\frac {{\rm d}^{2}}{{\rm d}{t}^{2}}}y \left( t \right) +{\it b2}\,{\frac {\rm d}{{\rm d}t}}y \left( t \right) +{\it c2}\,y \left( t \right) +A{\frac {\rm d}{{\rm d}t}}x \left( t \right) =0 \right\} }
\]