Question

Is 1,3,6,10..... an arithmetic progression.justify answer

Answer 1

no it is not because the common difference is not same in this AP between the terms .

d=T2-T1=T3-T2=T4-T3
so,d=3-1=6-3=10-6
d=2=3=4, is not possible.

so this doesn't form an AP.

Answer 2

1. This was not an ap because the common difference is changed on a2 and so on. D=a2-a1 ; on a3 the common difference is Chanded .