Question

Find the sum of first 51 term of an ap whose second and third term are 14 and 18 respectively. NO SPAM AND PROPER ANSWER.

Answer 1

Answer:

let first term be 'a' and common difference'd'

ATQ

a+d=14. (1)

a+2d=18. (2)

From 1 and 2

a=10&d=4

Answer 2

Answer:

5610

Step-by-step explanation:

2nd term  = 14   ⇒  a + d  = 14      equ (1)

3rd term = 18     ⇒  a + 2d = 18     equ (2)

on solving (1) & (2)   we get  d  = 4

(1) ⇒ a + d = 14

      a + 4  =14

      a   =  10

Sn =  n/2 ( 2a + (n-1) d  )

S51  =  51 /2  (2a + 50d )

       = 51 /2 ( 20 + 200)

      = 51/2  x 220

       = 5610