Setting You have...
(1)
Integrating (1) You obtain...
(2)
Kind regards
I apologize for the fact that a [stupid...] 'competition stress' often produces incomplete or 'impossible to undestand' answers...
Setting we have...
(1)
... and the first step is terminated. The (1) can be written as an ordinary first order DE as follows...
(2)
... with the 'condition' and its solution is...
(3)
Kind regards