\[ y''(x)-f(x) y(x)=0 \] ✗ Mathematica : cpu = 0.116518 (sec), leaf count = 0
, could not solve
DSolve[-(f[x]*y[x]) + Derivative[2][y][x] == 0, y[x], x]
✗ Maple : cpu = 0. (sec), leaf count = 0
, result contains DESol or ODESolStruc
\[y \relax (x ) = \mathit {DESol}\left (\left \{-f \relax (x ) \textit {\_Y} \relax (x )+\frac {d^{2}}{d x^{2}}\textit {\_Y} \relax (x )\right \}, \left \{\textit {\_Y} \relax (x )\right \}\right )\]