For the following $APs$,$-5, -1, 3, 7, \ldots$,write the first term and the common difference.

$A$ manufacturer of $TV$ sets produced $600$ sets in the third year and $700$ sets in the seventh year. Assuming that the production increases uniformly by a fixed number every year,find the production in the $1^{st}$ year.

Write the first four terms of the $AP,$ when the first term $a$ and the common difference $d$ are given as follows: $a = 10, d = 10.$

Which term of the $AP: 21, 18, 15, \ldots$ is $-81$? Also,is any term $0$? Give reason for your answer.

The sum of the third and the seventh terms of an $AP$ is $6$ and their product is $8$. Find the sum of the first sixteen terms of the $AP$.

In the following arithmetic progression $(AP)$,find the missing terms in the boxes: $\square, 13, \square, 3$.