\[ 4 y^{(3)}(x)-8 y''(x)-11 y'(x)-3 y(x)+18 e^x=0 \] ✓ Mathematica : cpu = 0.0284486 (sec), leaf count = 37
\[\left \{\left \{y(x)\to e^{-x/2} \left (c_2 x+c_3 e^{7 x/2}+c_1+e^{3 x/2}\right )\right \}\right \}\]
✓ Maple : cpu = 0.021 (sec), leaf count = 23
\[ \left \{ y \left ( x \right ) = \left ( {\it \_C3}\,x+{\it \_C2} \right ) {{\rm e}^{-{\frac {x}{2}}}}+{\it \_C1}\,{{\rm e}^{3\,x}}+{{\rm e}^{x}} \right \} \]