The affixes ktavā and ṇamul come after the root bhū 'to be' when the word anvak in the sense of being favourably disposed, is in composition.,
The word आनुलोम्य means 'agreeable, friendly or favourably disposed, or doing according to the wish of another'. Thus अन्वग्भूय—अन्वग्भूत्वा or अन्वग् भावमास्ते 'he is favourably disposed'.
Why do we say 'when meaning friendly' ? Observe अन्वग्भूत्वा तिष्ठति 'he remains behind'.,