Question

find the sum of n terms of the series 1+5+12+22+35+ ...​

Answer 1

Answer:

here,

a=1

d= a2- a1

= 5-1

= 4

and a3-a2

= 12-5

=7

so, a2-a1is not equals to a3-a2

so, it is not an ap

plz follow!!!!!!!!