For questions 3. and 4., consider the sequence $(u_n)$ defined on $\mathbb{N}$ by: $$u_0 = 15 \text{ and for every natural number } n : u_{n+1} = 1{,}2\, u_n + 12.$$
Consider the sequence $(v_n)$ defined on $\mathbb{N}$ by: $v_n = u_n + 60$.
The sequence $(v_n)$ is: a. a decreasing sequence; b. a geometric sequence with common ratio 1,2; c. an arithmetic sequence with common difference 60; d. a sequence that is neither geometric nor arithmetic.