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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

Syeda

Member since Jan 25, 2017

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

Member since Apr 11, 2014

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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