For you all: thanks very much! ...
... the purpose of my question is related to the following differential equation...
(1)
... that has been proposed in another section...
A 'brute force approach' to (1) seems to have little chances but if we operate the change of variables , thanks to the formula you have supplied, we have...
(2)
... and the (1) becomes...
(3)
... that is much more tractable [linear DE with constant coefficients...] and has as solution...
(4)
thanks again! ...
Kind regards