Answer :
Tn=a+(n-1)d
so 7n=a+(n-1)d
now T1=7*1=7
T2=14
T3=21
so Tn-T(n-1)=7n-7(n-1)
=7n-7n+7
s0 difference D=7
so Tn is A.P
7,14,21,28,35,42,49,...............................
so 7n=a+(n-1)d
now T1=7*1=7
T2=14
T3=21
so Tn-T(n-1)=7n-7(n-1)
=7n-7n+7
s0 difference D=7
so Tn is A.P
7,14,21,28,35,42,49,...............................