Odpowiedź:
[tex]a_{n} = a_{1} + (n - 1)r \\a_{6}=a_{1} + 5r \\ 28 = 3 + 5r \\ 25 = 5r \\ r = 5[/tex]
[tex] a_{n} = a_{1} + (n - 1)r \\ a_{n} = 3 + (n - 1) \times 5 = \\ = 3 + 5n - 5 \\ \\ a_{n} = -2 + 5n[/tex]
