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Ex 5.4, 1 (Optional) - Which term of AP 121, 117, 113 is first negativ

Ex 5.4, 1 (Optional) - Chapter 5 Class 10 Arithmetic Progressions - Part 2

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Ex 5.4, 1 (Optional) Which term of the AP : 121, 117, 113, . . ., is its first negative term? [Hint : Find n for an < 0] Given AP is 121, 117, 113,…… Here, a = 121 d = 117 − 121 = −4 Let the nth term of the AP be its first negative term. an < 0 a + (n − 1) d < 0 Putting a = 121 and d = −4 121 + (n − 1) (−4) < 0 121 − 4n + 4 < 0 125 − 4n < 0 125 < 4n 4n > 125 n > 125/4 n > 31.25 Since, the first negative term is greater than 31.25, it is 32nd term.

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Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 12 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.