For the following A.P.'s write the first term and the common difference:
`-5,-1,3,7……`

Answer

To solve the problem, we need to identify the first term and the common difference of the given arithmetic progression (A.P.): `-5, -1, 3, 7...`.

### Step-by-Step Solution:

1. **Identify the First Term (A1)**:
- The first term of the A.P. is the first number in the sequence.
- Here, the first term \( A_1 = -5 \).

2. **Identify the Common Difference (D)**:
- The common difference \( D \) can be calculated by subtracting the first term from the second term, or any subsequent term from its preceding term.
- We can calculate \( D \) using the formula:
\[ D = A_2 - A_1 \]
- Where \( A_2 \) is the second term and \( A_1 \) is the first term.
- From the sequence, \( A_2 = -1 \) and \( A_1 = -5 \).
- Thus, we calculate:
\[ D = -1 - (-5) = -1 + 5 = 4 \]

3. **Conclusion**:
- The first term \( A_1 \) is \( -5 \).
- The common difference \( D \) is \( 4 \).

### Final Answer:
- First Term: \( -5 \)
- Common Difference: \( 4 \)