\[ \left \{x'(t)=4 x(t),y'(t)=x(t)-2 y(t),z'(t)=x(t)-4 y(t)+z(t)\right \} \] ✓ Mathematica : cpu = 0.00739 (sec), leaf count = 94
DSolve[{Derivative[1][x][t] == 4*x[t], Derivative[1][y][t] == x[t] - 2*y[t], Derivative[1][z][t] == x[t] - 4*y[t] + z[t]},{x[t], y[t], z[t]},t]
\[\left \{\left \{x(t)\to c_1 e^{4 t},y(t)\to \frac {1}{6} c_1 e^{-2 t} \left (e^{6 t}-1\right )+c_2 e^{-2 t},z(t)\to \frac {1}{9} c_1 e^{-2 t} \left (e^{3 t}+e^{6 t}-2\right )-\frac {4}{3} c_2 e^{-2 t} \left (e^{3 t}-1\right )+c_3 e^t\right \}\right \}\] ✓ Maple : cpu = 0.103 (sec), leaf count = 50
dsolve({diff(x(t),t) = 4*x(t), diff(y(t),t) = x(t)-2*y(t), diff(z(t),t) = x(t)-4*y(t)+z(t)})
\[\left \{x \left (t \right ) = c_{3} {\mathrm e}^{4 t}, y \left (t \right ) = \frac {c_{3} {\mathrm e}^{4 t}}{6}+c_{2} {\mathrm e}^{-2 t}, z \left (t \right ) = \frac {c_{3} {\mathrm e}^{4 t}}{9}+c_{1} {\mathrm e}^{t}+\frac {4 c_{2} {\mathrm e}^{-2 t}}{3}\right \}\]