\[ \left \{x''(t)-x'(t)+y'(t)=0,x''(t)-x(t)+y''(t)=0\right \} \] ✓ Mathematica : cpu = 0.0320885 (sec), leaf count = 420
\[\left \{\left \{x(t)\to -\frac {1}{5} c_1 e^{\frac {t}{2}-\frac {\sqrt {5} t}{2}} \left (\sqrt {5} e^{\sqrt {5} t}-5 e^{\frac {\sqrt {5} t}{2}+\frac {t}{2}}-\sqrt {5}\right )+\frac {c_2 e^{\frac {t}{2}-\frac {\sqrt {5} t}{2}} \left (e^{\sqrt {5} t}-1\right )}{\sqrt {5}}-\frac {1}{10} c_4 e^{\frac {t}{2}-\frac {\sqrt {5} t}{2}} \left (5 e^{\sqrt {5} t}+\sqrt {5} e^{\sqrt {5} t}-10 e^{\frac {\sqrt {5} t}{2}+\frac {t}{2}}+5-\sqrt {5}\right ),y(t)\to -\frac {1}{10} c_1 e^{-\frac {\sqrt {5} t}{2}} \left (-5 e^{t/2}-\sqrt {5} e^{t/2}+10 e^{\frac {\sqrt {5} t}{2}}-5 e^{\sqrt {5} t+\frac {t}{2}}+\sqrt {5} e^{\sqrt {5} t+\frac {t}{2}}\right )+\frac {1}{10} c_2 e^{-\frac {\sqrt {5} t}{2}} \left (-5 e^{t/2}-\sqrt {5} e^{t/2}+10 e^{\frac {\sqrt {5} t}{2}}-5 e^{\sqrt {5} t+\frac {t}{2}}+\sqrt {5} e^{\sqrt {5} t+\frac {t}{2}}\right )+\frac {c_4 e^{\frac {t}{2}-\frac {\sqrt {5} t}{2}} \left (e^{\sqrt {5} t}-1\right )}{\sqrt {5}}+c_3\right \}\right \}\] ✓ Maple : cpu = 0.092 (sec), leaf count = 71
\[\left \{\left \{x \left (t \right ) = c_{1} {\mathrm e}^{t}-\frac {c_{3} \left (\sqrt {5}+1\right ) {\mathrm e}^{\frac {\left (\sqrt {5}+1\right ) t}{2}}}{2}+\frac {c_{4} \left (\sqrt {5}-1\right ) {\mathrm e}^{-\frac {\left (\sqrt {5}-1\right ) t}{2}}}{2}, y \left (t \right ) = c_{3} {\mathrm e}^{\frac {\left (\sqrt {5}+1\right ) t}{2}}+c_{4} {\mathrm e}^{-\frac {\left (\sqrt {5}-1\right ) t}{2}}+c_{2}\right \}\right \}\]