Question

if the 9th term of an ap is zero then show that the 29 term is twice the 19th term

Answer 1

Given that
The 9th term of the A.P = 0
Therefore
a + 8d = 0
a = - 8d

To prove 29th term is twice of the 19th term
So
a + 28d = 2(a + 18d)
a + 28d = 2a + 36d
Substituting the value of a = - 8d
- 8d + 28d = 2*-8d + 36d
20d = 36d - 16d
20d = 20d

Hence proved.

Hope this helps you.