What did I do wrong here?
The correct answer given by the professor is:
The standard approach for solving the DE...
(1)
... has as first step the division of both terms of (1) by obtaining...
(2)
... and then the substution...
(3)
... so that the new DE in z is...
(4)
... which is linear and easy enough to solve...
... the minor problem is that (4) seems not the same You obtained that is...
(5)
Kind regards