Question

The sum of 2nd term and 7th term of an A.P. is 30.If its 15th term is 1 less than twice of the 8th term,find the A.P.

Answer 1

a + d + a + 6d = 30
2a + 7d = 30
a + 14d + 1 = 2 (a + 7d)
a + 14d + 1 = 2a + 14d
a = 1
d = 4
ap is 1,5,9,13.......

Answer 2

Here is your solution

Given:-

t2+t7=30
=>a+d+a+6d=30
=>2a+7d=30..................... (1)

A/q
15th term=2×8th term-1
=>a+14d=2×(a+7d)-1
=>a+14d=2a+14d-1
=>14d-14d+1=2a-a
=>1=a

Putting the value of a in equation (1)

2a×7d=30
2×1+7d=30
2+7d=30
7d=30-2
7d=28
d=4

A.p are a,a+d,a+2d,a+3d,a+4d

=>A.p are 1,5,9,13.........

HOPE IT HELPS YOU