If the 9th term of an AP is 0, prove that its 29th term is twice its 19th term.

Asked by Palak Shrivastava | 11th Nov, 2013, 06:36: AM

Expert Answer:

Let a and d respectively be the first term and common difference of the AP.

Given a9 = 0

So, a + (9-1)d = 0

a+8d=0

a= -8d

 

Now, 29th term = a+28d

=-8d+28d

= 20d = 2 x 10d

= 2(-8d + 18d)
=2(a+18d)
= 2 x 19th term
 
Thus, the 29th term of the AP is twice the 19th term.

Answered by  | 11th Nov, 2013, 09:31: AM

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