deriv SD cv (342) ashtadhyayi.com hei.de L 342 ETT STT a 7.2.92 ALPH OLDHOMEPAGE NEWHOMEPAGE

yuvAvau dvivacane

युवावौ द्विवचने ONPANINI 72092

(Replace /yuSm /asm) with yuva युव Ava आव when meaning dual.

/yuSmad- + /bhyAm
→ yuSma युष्म + /bhyAm by << zeSelopaH
→ yuva युव + a अ + /bhyAm by this rule
→ yuva युव + /bhyAm by atoguNe
→ yuvA युवा + /bhyAm by supica
→ !**yuvAbhyAm युवाभ्याम्

/asmad- + /bhyAm → !**AvAbhyAm आवाभ्याम्, same steps.

Why did you translate as "when meaning dual" instead of "before a dual /sup"?

Not same thing. These can be ifc and have a dual meaning while followed by a singular or plural /sup. See candravasu. See pratyayottar... 6>.