for an arthemetic progression S2n=3Sn then the value of S3n/Sn=??
alekhya , 8 Years ago
Grade 12th pass
Algebra> for an arthemetic progression S 2n =3S n ...
1 AnswersVikas TU
Last Activity: 8 Years ago
S2n=3Sn
[n + (2a + (2n -1)d)] = [3n/2 + 6a + 3nd -3d]
after solving ,
2a – d = -n/4 – nd/2.......................................(1)
S3n = [3n/2 + 2a + 3nd -d]
after substituting from eqn. (1)
S3n = 5n/2[d+ 1/2]
and Sn = 2a – d + 2nd + n
after substituting rom eqn. (1)
= 3n/2[d + 1/2]
[n + (2a + (2n -1)d)] = [3n/2 + 6a + 3nd -3d]
after solving ,
2a – d = -n/4 – nd/2.......................................(1)
S3n = [3n/2 + 2a + 3nd -d]
after substituting from eqn. (1)
S3n = 5n/2[d+ 1/2]
and Sn = 2a – d + 2nd + n
after substituting rom eqn. (1)
= 3n/2[d + 1/2]
Hence,
S3n/Sn = 5/3
S3n/Sn = 5/3
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