Question

in a certain A.P the 24th term is twice the 10th term . prove that the 72nd term is twice the 30th term

Answer 1

ur ques is wrong it is not 30th term it is 34th term
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given a24=2(a10)
        a+23d=2(a+9d)
        a+23d=2a+18d
         a-5d=0       ⇒a=5d         ---1
taking the eq that needed to be proved
       a72=2(a34)
   a+71d=2(a+33d)                 ---2

from 1 substituting it in 2
then
  5d+71d=2(5d+33d)
        76d=2(38d)            ⇒ 76d=76d 
hence proved
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