\[ \left \{x'(t)=-5 x(t)-2 y(t),y'(t)=x(t)-7 y(t)\right \} \] ✓ Mathematica : cpu = 0.0089104 (sec), leaf count = 59
DSolve[{Derivative[1][x][t] == -5*x[t] - 2*y[t], Derivative[1][y][t] == x[t] - 7*y[t]},{x[t], y[t]},t]
\[\left \{\left \{x(t)\to c_1 e^{-6 t} (\sin (t)+\cos (t))-2 c_2 e^{-6 t} \sin (t),y(t)\to c_1 e^{-6 t} \sin (t)+c_2 e^{-6 t} (\cos (t)-\sin (t))\right \}\right \}\] ✓ Maple : cpu = 0.046 (sec), leaf count = 44
dsolve({diff(x(t),t) = -5*x(t)-2*y(t), diff(y(t),t) = x(t)-7*y(t)})
\[\left \{x \left (t \right ) = {\mathrm e}^{-6 t} \left (c_{1} \sin \left (t \right )+c_{2} \cos \left (t \right )\right ), y \left (t \right ) = -\frac {{\mathrm e}^{-6 t} \left (\left (c_{1}-c_{2}\right ) \cos \left (t \right )-\sin \left (t \right ) \left (c_{1}+c_{2}\right )\right )}{2}\right \}\]