Question

The 8th term of an AP is 20 and the 15th term is 12 more than the 11th term. Find the AP

Answer 1

Let the first term of the AP be a and Cd = d
So 8th term = a + (8-1)d =a +7d =20 (1)
And 15th term = a +14d
As from condition a +14d = a +10d +12 (2)
So from (2) , we get d = 3
Using d =3, in (10, we get
a + 21 =20
Or a =-1
Hence the AP is -1 , 2 , 5 .........