\[ -a y(x)-b+y''(x)^2=0 \] ✓ Mathematica : cpu = 1.14372 (sec), leaf count = 201
\[\left \{\text {Solve}\left [\frac {(a y(x)+b)^2 \left (1-\frac {4 (a y(x)+b)^{3/2}}{3 a c_1}\right ) \, _2F_1\left (\frac {1}{2},\frac {2}{3};\frac {5}{3};\frac {4 (b+a y(x))^{3/2}}{3 a c_1}\right ){}^2}{a^2 \left (-\frac {4 (a y(x)+b)^{3/2}}{3 a}+c_1\right )}=(x+c_2){}^2,y(x)\right ],\text {Solve}\left [\frac {(a y(x)+b)^2 \left (1+\frac {4 (a y(x)+b)^{3/2}}{3 a c_1}\right ) \, _2F_1\left (\frac {1}{2},\frac {2}{3};\frac {5}{3};-\frac {4 (b+a y(x))^{3/2}}{3 a c_1}\right ){}^2}{a^2 \left (\frac {4 (a y(x)+b)^{3/2}}{3 a}+c_1\right )}=(x+c_2){}^2,y(x)\right ]\right \}\] ✓ Maple : cpu = 0.799 (sec), leaf count = 173
\[\left \{-c_{2}-x +\int _{}^{y \left (x \right )}\frac {\sqrt {3}\, a}{\sqrt {\left (4 \sqrt {\textit {\_a} a +b}\, \textit {\_a} a -c_{1}+4 \sqrt {\textit {\_a} a +b}\, b \right ) a}}d \textit {\_a} = 0, -c_{2}-x +\int _{}^{y \left (x \right )}-\frac {3 a}{\sqrt {-12 \left (-\frac {c_{1}}{4}+\left (\textit {\_a} a +b \right )^{\frac {3}{2}}\right ) a}}d \textit {\_a} = 0, -c_{2}-x +\int _{}^{y \left (x \right )}\frac {3 a}{\sqrt {-12 \left (-\frac {c_{1}}{4}+\left (\textit {\_a} a +b \right )^{\frac {3}{2}}\right ) a}}d \textit {\_a} = 0, -c_{2}-x +\int _{}^{y \left (x \right )}-\frac {\sqrt {3}\, a}{\sqrt {\left (4 \sqrt {\textit {\_a} a +b}\, \textit {\_a} a -c_{1}+4 \sqrt {\textit {\_a} a +b}\, b \right ) a}}d \textit {\_a} = 0, y \left (x \right ) = -\frac {b}{a}\right \}\]