NCERT Solutions for Class 10 Maths Chapter 5
Important NCERT Questions
Arithmetic Progression
NCERT Books for Session 2022-2023
CBSE Board and UP Board Others state Board
EXERCISE 5.4
Page No:115
Questions No:1
Which term of the AP : 121, 117, 113, . . ., is its first negative term?
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Here, a = 121 and d = 117 – 121 = – 4.
Let, a_n be the first negative term of this AP.
⇒ a_n < 0
⇒ a + (n – 1)d < 0
⇒ 121 + (n -1)(-4) < 0
⇒ 121 – 4n + 4 < 0
⇒ 125 125/4
⇒ n > 31.25
⇒ n = 32
Hence, 32nd term of the AP: 121, 117, 113 … is its first negative term.