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The 24th term of an A.P. is twice its 10th term. Show that its 72nd term is 4 times its 15th term. |
Answer» Given: a24 = 2a10 a +23d = 2(a +9d) 5d = a (i) To Prove: a72 = 4a15 Proof: L.H.S. = a72 = a +71d = 5d +71d [from (i)] = 76d R.H.S = 4a15 = 4(a +14d) = 4a +56d = 4(5d) +56d [from (i)] = 20d +56d = 76d Since, L.H.S = R.H.S. Hence proved |
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