2. Find the eighteenth term of the A. P. : 1, 7, 13, 19, ..... (2 marks)
Sol. For the given A.P. 1, 7, 13, 19, .....
Here, a = t1 = 1
d = t2 – t1 = 7 – 1 = 6
We know,
tn = a + (n – 1) d
t18 = a + (18 – 1) d
t18 = 1 + 17 (6)
t18 = 1 + 102
t18 = 103
Eighteenth term of A.P. is 103.
