\[ \left \{x'(t)-x(t)+2 y(t)=0,x''(t)-2 y'(t)=2 t-\cos (2 t)\right \} \] ✓ Mathematica : cpu = 0.223118 (sec), leaf count = 116
\[\left \{\left \{x(t)\to 8 c_1 e^{t/2}+8 c_2 e^{t/2}-c_2-t^2-4 t+\frac {1}{34} \sin (2 t)+\frac {2}{17} \cos (2 t)-8,y(t)\to 2 c_1 e^{t/2}+2 c_2 e^{t/2}-\frac {c_2}{2}-\frac {t^2}{2}-t+\frac {9}{68} \sin (2 t)+\frac {1}{34} \cos (2 t)-2\right \}\right \}\]
✓ Maple : cpu = 0.11 (sec), leaf count = 69
\[ \left \{ \left \{ x \left ( t \right ) =2\,{\it \_C1}\,{{\rm e}^{t/2}}-{t}^{2}+{\frac {\sin \left ( 2\,t \right ) }{34}}+{\frac {2\,\cos \left ( 2\,t \right ) }{17}}-4\,t+{\it \_C2},y \left ( t \right ) ={\frac {{\it \_C1}}{2}{{\rm e}^{{\frac {t}{2}}}}}-t+{\frac {\cos \left ( 2\,t \right ) }{34}}+{\frac {9\,\sin \left ( 2\,t \right ) }{68}}+2-{\frac {{t}^{2}}{2}}+{\frac {{\it \_C2}}{2}} \right \} \right \} \]