\[ f(x) \left (y(x)^2-x^2\right )+x y'(x)=0 \] ✗ Mathematica : cpu = 16.6203 (sec), leaf count = 0 , could not solve
DSolve[f[x]*(-x^2 + y[x]^2) + x*Derivative[1][y][x] == 0, y[x], x]
✗ Maple : cpu = 0. (sec), leaf count = 0 , could not solve
dsolve(x*diff(y(x),x)+f(x)*(y(x)^2-x^2) = 0,y(x))