Answer:

1 is an ap because their common difference is same

next 2 terms 26+7=33 , 33+7=40

Answer:

1. t1=5 t2=12 t3=19 t4=26

t1=5 t2=12 t3=19 t4=26 t2 -t1= d

t1=5 t2=12 t3=19 t4=26 t2 -t1= d 12- 5= 7

t3-t2= 19- 12 =7......

and accordingly as it has a common difference it is a A.P

2. t1=1 t2=1 t3=2 t4=2 t5=3 t6=3

● t2 -t1

= 1 -1

= 0

● t3-t2

= 2 -1

= 1

● t4-t3

=2- 2

=0

●t5- t4

=3 -2

= 1

● t6 -t5

= 3 -3

= 0

therefore it is not an A.P as its difference is not common .