\[ y''(x)=-\frac {y(x)}{(a x+b)^4} \] ✓ Mathematica : cpu = 0.0650199 (sec), leaf count = 59
\[\left \{\left \{y(x)\to c_1 e^{\frac {i}{a (a x+b)}} (a x+b)-\frac {1}{2} i c_2 e^{-\frac {i}{a (a x+b)}} (a x+b)\right \}\right \}\] ✓ Maple : cpu = 0.059 (sec), leaf count = 39
\[y \relax (x ) = \left (a x +b \right ) \left (c_{2} \cos \left (\frac {1}{a \left (a x +b \right )}\right )+c_{1} \sin \left (\frac {1}{a \left (a x +b \right )}\right )\right )\]