\left\{a \left(x'(t)-y'(t)\right)+\text{b1} x(t)+x''(t)=\text{c1} e^{i \omega  t},a \left(y'(t)-x'(t)\right)+\text{b2} y(t)+y''(t)=\text{c2} e^{i \omega  t}\right\}