\[ \boxed { {\frac {{\rm d}^{2}}{{\rm d}{x}^{2}}}y \left ( x \right ) -7\,{\frac {\rm d}{{\rm d}x}}y \left ( x \right ) - \left ( y \left ( x \right ) \right ) ^{3/2}+12\,y \left ( x \right ) =0} \]
Mathematica: cpu = 22.518860 (sec), leaf count = 29 \[ \text {DSolve}\left [y''(x)-7 y'(x)-y(x)^{3/2}+12 y(x)=0,y(x),x\right ] \]
Maple: cpu = 0.811 (sec), leaf count = 57 \[ \left \{ y \left ( x \right ) ={\it ODESolStruc} \left ( {\it \_a},[ \left \{ \left ( {\frac {\rm d}{{\rm d}{\it \_a}}}{\it \_b} \left ( { \it \_a} \right ) \right ) {\it \_b} \left ( {\it \_a} \right ) -7\,{\it \_b} \left ( {\it \_a} \right ) -{{\it \_a}}^{{\frac {3}{2}}}+12\,{\it \_a}=0 \right \} , \left \{ {\it \_a}=y \left ( x \right ) ,{\it \_b} \left ( {\it \_a} \right ) ={\frac {\rm d}{{\rm d}x}}y \left ( x \right ) \right \} , \left \{ x=\int \! \left ( {\it \_b} \left ( {\it \_a} \right ) \right ) ^{-1}\,{\rm d}{\it \_a}+{\it \_C1},y \left ( x \right ) ={\it \_a} \right \} ] \right ) \right \} \]