For the following A.P's write the first term and common difference:

- 5, - 1, 3, 7, ...

In general, for an AP a₁, a₂, . . . .,a_n, we have

d = a_k+1 - a_k

where a_k+1 and a_k are the (k+1)^th and k^th terms respectively.

For the list of numbers: - 5, - 1, 3, 7, ...

a₂ – a₁ = -1 – (-5) = -1 + 5 = 4

a₃ – a₂ = 3 – (-1) = 3 + 1 = 4

a₄ – a₃ = 7 – 3 = 4

Here, the difference of any two consecutive terms in each case is -4. So, the given list is an AP whose first term a is -5 and common difference d is 4.