Question

the 8th term of an ap is zero prove that its 38 term is triple of its 18th term

Answer 1

given
T8=0
=> a+7d =0
=> a= -7d----------(1)
T18= a+17d
putting a=-7d
=-7d+17d
=10d-----(2)

T38 = a+37d
putting a=-7d from (1)
T38= -7d+37d
=30d
= 3(10d)
=3T8
hence proved