Show that the sequence defined by $a_n=5n-7$ is an $A.P.$, find its common difference.

Write the sequence with $n^{\text{th}}$ term $a_n=3+4n$. Show that the sequence forms $A.P.$

Write the sequence with $n^{\text{th}}$ term $a_n=6-n$.

Show that the above sequence forms AP.

Write the sequence with $n$th term:
$a_n=9-5n$

Show that the sequence form A.P.