Răspuns :
[tex]\displaystyle \\ \text{Numarul de ordine al unui termen din sir =} \\ \text{numarul de termeni de la primul termen pana la termenul dat inclusiv } \\ \\ a)~ Avem~sirul:~~1;~3;~5;~ \hdots ;~ 21 \\ \\ n = \frac{21 - 1}{2}+1 = 10+1 = \boxed{11~termeni } = \boxed{al~11-lea~termen } \\ \\ b)~ Avem~sirul:~~1;~3;~5;~ \hdots ;~ 441 \\ \\ n = \frac{441 - 1}{2}+1 = 220+1 = \boxed{221~termeni } = \boxed{al~221-lea~termen } [/tex]
[tex]\displaystyle \\ c)~ Avem~sirul:~~1;~3;~5;~ \hdots ;~ 9261 \\ \\ n = \frac{9261 - 1}{2}+1 = \\ \\ = \frac{9260}{2}+1 =4630+1 = \boxed{4631~termeni } = \boxed{al~4631-lea ~termen }[/tex]
