\[ y'(x)^n-f(x)^n (y(x)-a)^{n+1} (y(x)-b)^{n-1}=0 \] ✓ Mathematica : cpu = 0.166825 (sec), leaf count = 86
\[\left \{\left \{y(x)\to \frac {-b n^n-a (a-b)^n \left (\int _1^x(-1)^{1+\frac {1}{n}} f(K[1])dK[1]+c_1\right ){}^n}{-n^n-(a-b)^n \left (\int _1^x(-1)^{1+\frac {1}{n}} f(K[1])dK[1]+c_1\right ){}^n}\right \}\right \}\] ✓ Maple : cpu = 0.67 (sec), leaf count = 55
\[y \relax (x ) = \frac {\left (-\frac {n}{\left (a -b \right ) \left (\int f \relax (x )d x +c_{1}\right )}\right )^{n} b -a}{-1+\left (-\frac {n}{\left (a -b \right ) \left (\int f \relax (x )d x +c_{1}\right )}\right )^{n}}\]