\[ 2 y(x) y''(x)-y'(x)^2-3 y(x)^4=0 \] ✓ Mathematica : cpu = 6.14685 (sec), leaf count = 129
\[\left \{\left \{y(x)\to \text {InverseFunction}\left [-\frac {2 \sqrt {\text {$\#$1}} \sqrt {\frac {\text {$\#$1}^3}{c_1}+1} \, _2F_1\left (\frac {1}{6},\frac {1}{2};\frac {7}{6};-\frac {\text {$\#$1}^3}{c_1}\right )}{\sqrt {\text {$\#$1}^3+c_1}}\& \right ][c_2+x]\right \},\left \{y(x)\to \text {InverseFunction}\left [\frac {2 \sqrt {\text {$\#$1}} \sqrt {\frac {\text {$\#$1}^3}{c_1}+1} \, _2F_1\left (\frac {1}{6},\frac {1}{2};\frac {7}{6};-\frac {\text {$\#$1}^3}{c_1}\right )}{\sqrt {\text {$\#$1}^3+c_1}}\& \right ][c_2+x]\right \}\right \}\] ✓ Maple : cpu = 0.069 (sec), leaf count = 49
\[ \left \{ \int ^{y \left ( x \right ) }\!{\frac {1}{\sqrt {{{\it \_a}}^{4}+{\it \_a}\,{\it \_C1}}}}{d{\it \_a}}-x-{\it \_C2}=0,\int ^{y \left ( x \right ) }\!-{\frac {1}{\sqrt {{{\it \_a}}^{4}+{\it \_a}\,{\it \_C1}}}}{d{\it \_a}}-x-{\it \_C2}=0 \right \} \]