Question

Identify if a given sequence of numbers is an arithmetic progression or not.

a) $8,17,26,35,...$

b) $-4,-9,-16,-25,..$

Answer 1

(a) $8,17,26,35$

We can see that $17-8=26-17=35-26=9=d$

$\therefore$ it is an $AP$

(b) $-4,-9,-16,-25$

We can see $-9+4\ne -16+9\ne -25+16\ne d$

$\therefore$ We can see that there is no common difference between the sequence $\therefore$ it is not an $AP$.