The sequence is defined by the formula:

$a_n = -2n + 9$

We need to find the first four terms, starting with $n = 1$.

1. For $n = 1$: $a_1 = -2(1) + 9 = -2 + 9 = 7$

2. For $n = 2$: $a_2 = -2(2) + 9 = -4 + 9 = 5$

3. For $n = 3$: $a_3 = -2(3) + 9 = -6 + 9 = 3$

4. For $n = 4$: $a_4 = -2(4) + 9 = -8 + 9 = 1$

Thus, the first four terms of the sequence are: $\boxed{7}, \boxed{5}, \boxed{3}, \boxed{1}$

Would you like any additional explanations or details?

Here are 5 related questions to deepen your understanding:

1. What happens to the sequence if we extend it to $n = 5$ or beyond?
2. How would the sequence change if the formula were $a_n = -3n + 9$?
3. Can you find a general pattern for the sequence when $n$ is any positive integer?
4. How would the sequence look if we started with $n = 0$ instead of $n = 1$?
5. What type of sequence is represented by this formula, and how does it differ from geometric sequences?

Tip: A sequence that decreases by the same amount each time, like this one, is known as an arithmetic sequence.