Given A.P is 7, 10, 13,…

Here, a₁ = a = 7, a₂ = 10

Common difference, d = a₂ – a₁ = 10 – 7 = 3

We know, a_n = a + (n – 1)d where a is first term or a₁ and d is common difference and n is any natural number

∴ a_n = 7 + (n – 1)3

⇒ a_n = 7 + 3n – 3

⇒ a_n = 3n + 4

Now, to find whether 68 is a term of this A.P. or not

Put a_n = 68

∴ 3n + 4 = 68

⇒ 3n = 68 – 4

⇒ 3n = 64

is not a natural number

Hence, 68 is not a term of given A.P.