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Rejitha Krishnan RG

Sep 23, 2014

# Prove that its 29th term is double the 19th term.

if 9th term of an AP is zero ,prove that its 29th term is double the 19th term

Ligandro singh

Member since Apr 1, 2017

A9 = 0  Let A be the first term of this Ap and D be the common difference . Therefore A9 = A + (9-1)d (eq  1) = 0         Now A29 = A + 28D and A19 = A + 18D            Now 2 × A19 = 2A + 36 D = A + 28D + A + 8D and we know that A + 8D = 0 from eq 1. Therefore 2 × A19 = A + 28D = A29

Syeda

Answer. In A.P the first term� = a and common difference = d. Given that� 9th term of an A.P. is 0. Therefore t9 = 0 ⇒ a + 8d = 0 ⇒ a = -8d� --------------(1) We have to prove that t29 = 2 t19. t19 = a + 18d = -8d + 18d = 10d������� [� from (1) ] t29� = a + 28d = -8d + 28d = 20d������� [� from (1) ] t29� = 2 x 10d = 2 x t19 ∴ t29� = 2 x t19 . SME Approved

Raghunath Reddy

Sol: In A.P the first term  = a and common difference = d. Given that  9th term of an A.P. is 0. Therefore t9 = 0 ⇒ a + 8d = 0 ⇒ a = -8d  --------------(1) We have to prove that t29 = 2 t19. t19 = a + 18d = -8d + 18d = 10d        [  from (1) ] t29  = a + 28d = -8d + 28d = 20d        [  from (1) ] t29  = 2 x 10d = 2 x t19 ∴ t29  = 2 x t19 .
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