3. :
;
.;
.-.;
.
4. .. :
a b;
a b;
a b;
a→b.
5. , :
;
;
;
→;
≡.
Գ
__ _______________ 20__ .
__________________ ..., . . .
̲Ͳ ²
ֲ Ͳ Ͳ
____________________________________
( ) ________________
___________________________________________ ________________
4