\[ y''(x)=-b y(x) f(x)^{2 a}-\frac {a f'(x) y'(x)}{f(x)} \] ✗ Mathematica : cpu = 1.60517 (sec), leaf count = 0 , could not solve
DSolve[Derivative[2][y][x] == -(b*f[x]^(2*a)*y[x]) - (a*Derivative[1][f][x]*Derivative[1][y][x])/f[x], y[x], x]
✓ Maple : cpu = 0.021 (sec), leaf count = 37
\[\left \{y \left (x \right ) = c_{1} {\mathrm e}^{\int i \sqrt {b}\, f \left (x \right )^{a}d x}+c_{2} {\mathrm e}^{-\left (\int i \sqrt {b}\, f \left (x \right )^{a}d x \right )}\right \}\]