The Nūn of Dual and Plural

Noun Case Classes: Type 6 — Sound Masculine Plural and Related Forms

وَاعْلَمْ: أَنَّ نُونَ التَّثْنِيَةِ مَكْسُورَةٌ أَبَدًا، وَنُونَ جَمْعِ السَّلَامَةِ مَفْتُوحَةٌ أَبَدًا.
Translation: Know that the nūn of the dual always has kasra, whereas the nūn of the sound plural always has fatḥa.

طَالِبَانِ / طَالِبَيْنِ: final nūn with kasra.
طَالِبُونَ / طَالِبِينَ: final nūn with fatḥa.

This nūn normally remains when the word is not muḍāf.