\[ \left \{x'(t)=a x(t),y'(t)=b\right \} \] ✓ Mathematica : cpu = 0.0070033 (sec), leaf count = 22
\[\left \{\left \{x(t)\to c_1 e^{a t},y(t)\to b t+c_2\right \}\right \}\] ✓ Maple : cpu = 0.1 (sec), leaf count = 19
\[ \left \{ \left \{ x \left ( t \right ) ={\it \_C1}\,{{\rm e}^{at}},y \left ( t \right ) =bt+{\it \_C2} \right \} \right \} \]