Question

Cati termeni are sirul 17, 23, 29,........, 881?

Answer 1

[tex]\text{Ne dam seama ca termenii sirului sunt de forma }a_k=17+6\cdot k\\ \text{Prin urmare ultimul termen va fi:}\\ 17+6\cdot n=881\\ 6\cdot n=864\\ n=144\\ \text{In total sunt }144+1=\boxed{145}\ \text{termeni.}[/tex]