Question

The sum of first n terms of two aps are in ratio ( 3n+8 ) : ( 7n+15 ) . A

Answer 1

Step-by-step explanation:

Sum of n terms of an A.P =

$\frac{n}{2} (2a + (n - 1)d)$

nth term of an A.P = a+(n-1)d

Sum of first n terms of A.P (1) = 3n+8

First term of A.P (1) = 3(1) + 8 = 11

Sum of 1st two terms = 3(2) + 8 = 6 + 8 = 14

Second term = 14-11 = 3

Common difference = 3-11 = -8

Sum of first n terms of A.P (2) = 7n + 15

First term = 7(1)+15 = 22

Sum of 1st two terms = 7(2) + 15 = 14 + 15 = 29

Second term = 29-22 = 7

Common difference = 7-22 = -15