Answer:
The AP is 6, 11, 16, 21, 26, 31, 36, 41, 46, 51, 56, 61 ....
Step-by-step explanation:
The nth term = a1 + d(n - 1)
Sum of 5th and 9th terms
= a1 + 4d + a1 + 8d = 72
2a1 + 12d = 72.............(1)
Similarly:
a1 + 6d + a1 + 11d = 97
2a1 + 17d = 97..............(2)
Subtracting equation (1) from equation (2):
5d = 25
d = 5.
and , using equation (1), the first term
a1 = (72 - 12(5)) / 2
= 12/2
= 6.
