For the following A.P.'s write the first term and the common difference:
`3,-1,-3….`

Answer

To solve the problem, we need to identify the first term and the common difference of the given sequence: `3, -1, -3, ...`.

### Step-by-Step Solution:

1. **Identify the First Term (A1)**:
The first term of the sequence is the first number in the list.
\[ A_1 = 3 \]

2. **Identify the Second Term (A2)**:
The second term of the sequence is the second number in the list.
\[ A_2 = -1 \]

3. **Identify the Third Term (A3)**:
The third term of the sequence is the third number in the list.
\[ A_3 = -3 \]

4. **Calculate the Common Difference (D)**:
The common difference in an arithmetic progression (A.P.) is found by subtracting the first term from the second term or the second term from the third term.
- First, calculate the difference between the second term and the first term:
\[ D_1 = A_2 - A_1 = -1 - 3 = -4 \]
- Next, calculate the difference between the third term and the second term:
\[ D_2 = A_3 - A_2 = -3 - (-1) = -3 + 1 = -2 \]

5. **Conclusion**:
Since the common differences \(D_1\) and \(D_2\) are not equal (\(-4\) and \(-2\)), the sequence does not have a constant common difference. Therefore, it is not an arithmetic progression (A.P.).

### Final Answer:
- First Term (A1): \(3\)
- Common Difference (D): Not applicable (the sequence is not an A.P.)