Question

In an A.P., find the value of n, if a = – 5, d = 4 and an = 59.​

Answer 1

Answer:

Step-by-step explanation:

Given that,

a = - 5 and d = 4 and an = 59

We know that, an = a + ( n - 1 ) d

∴ 59 = - 5 + ( n - 1 ) 4

⇒ 59 = - 5 + 4n - 4 ( ∵ - × + = - )

⇒ 59 = - 5 - 4 + 4n

⇒ 59 = - 9 + 4n

⇒ 59 + 9 = 4n (∵transposing )

⇒ 68 = 4n

⇒ 68 / 4 = n ( ∵ transposing )

⇒ n = 17 is the answer.