\[ \boxed { {\frac {{\rm d}^{2}}{{\rm d}{x}^{2}}}y \left ( x \right ) -y \left ( x \right ) =0} \]
Mathematica: cpu = 0.003501 (sec), leaf count = 20 \[ \left \{\left \{y(x)\to c_1 e^x+c_2 e^{-x}\right \}\right \} \]
Maple: cpu = 0.016 (sec), leaf count = 15 \[ \left \{ y \left ( x \right ) ={\it \_C1}\,{{\rm e}^{-x}}+{\it \_C2}\,{ {\rm e}^{x}} \right \} \]