1. The problem is to find the general term $u_n$ of the sequence defined by $u_n = 2n + 1$. 2. The formula given is already the explicit formula for the $n$-th term of the sequence: $$u_n = 2n + 1$$ where $n$ is the term number. 3. This means for any term number $n$, you multiply $n$ by 2 and then add 1 to get the term value. 4. For example, to find $u_1$, substitute $n=1$: $$u_1 = 2(1) + 1 = 2 + 1 = 3$$ 5. To find $u_5$, substitute $n=5$: $$u_5 = 2(5) + 1 = 10 + 1 = 11$$ 6. This sequence is an arithmetic sequence with common difference 2, starting at 3. Final answer: $$u_n = 2n + 1$$