2) an = 6n-1

a) a4 = 6 * 4 - 1 = 23

б) a12 = 6 * 12 - 1 = 71

в) a100 = 6 * 100 - 1 = 599

г) ak = 6 * k - 1 = 6k - 1

д)ak+1 = 6 * (k + 1) - 1 = 6k + 6 - 1 = 6k + 5

3) an = n²

1² = 1

2² = 4

3² = 9

4² = 16

5² = 25