\[ 2 y(x) y''(x)-y'(x)^2-3 y(x)^4=0 \] ✓ Mathematica : cpu = 10.4062 (sec), leaf count = 285
\[\left \{\left \{y(x)\to \text {InverseFunction}\left [-\frac {2 i \text {$\#$1}^{3/2} \sqrt {(-1)^{5/6} \left (\frac {\sqrt [3]{-c_1}}{\text {$\#$1}}-1\right )} \sqrt {\frac {\left (-c_1\right ){}^{2/3}}{\text {$\#$1}^2}+\frac {\sqrt [3]{-c_1}}{\text {$\#$1}}+1} F\left (\sin ^{-1}\left (\frac {\sqrt {-\frac {i \sqrt [3]{-c_1}}{\text {$\#$1}}-(-1)^{5/6}}}{\sqrt [4]{3}}\right )|\sqrt [3]{-1}\right )}{\sqrt [4]{3} \sqrt [3]{-c_1} \sqrt {\text {$\#$1}^3+c_1}}\& \right ]\left [c_2+x\right ]\right \},\left \{y(x)\to \text {InverseFunction}\left [\frac {2 i \text {$\#$1}^{3/2} \sqrt {(-1)^{5/6} \left (\frac {\sqrt [3]{-c_1}}{\text {$\#$1}}-1\right )} \sqrt {\frac {\left (-c_1\right ){}^{2/3}}{\text {$\#$1}^2}+\frac {\sqrt [3]{-c_1}}{\text {$\#$1}}+1} F\left (\sin ^{-1}\left (\frac {\sqrt {-\frac {i \sqrt [3]{-c_1}}{\text {$\#$1}}-(-1)^{5/6}}}{\sqrt [4]{3}}\right )|\sqrt [3]{-1}\right )}{\sqrt [4]{3} \sqrt [3]{-c_1} \sqrt {\text {$\#$1}^3+c_1}}\& \right ]\left [c_2+x\right ]\right \}\right \}\]
✓ Maple : cpu = 0.121 (sec), leaf count = 49
\[ \left \{ \int ^{y \left ( x \right ) }\!{\frac {1}{\sqrt {{{\it \_a}}^{4}+{\it \_a}\,{\it \_C1}}}}{d{\it \_a}}-x-{\it \_C2}=0,\int ^{y \left ( x \right ) }\!-{\frac {1}{\sqrt {{{\it \_a}}^{4}+{\it \_a}\,{\it \_C1}}}}{d{\it \_a}}-x-{\it \_C2}=0 \right \} \]