1. Which term of the AP: 121, 117, 113, . . ., is its first negative term? [Hint: Find n for an < 0]
1. Which term of the AP: 121, 117, 113, . . ., is its first negative term? [Hint: Find n for an < 0]
Harshit Singh , 4 Years ago
Grade 12th pass
10 grade maths> 1. Which term of the AP: 121, 117, 113, ....
1 AnswersPawan Prajapati
Given the AP series is 121, 117, 113, . . .,
Thus, first term, a = 121
Common difference, d = 117-121= -4
By the nth term formula,
an = a+(n −1)d
Therefore,
an = 121+(n−1)(-4)
= 121-4n+4
=125-4n
To find the first negative term of the series, an < 0
Therefore,
125-4n < 0
125 < 4n
n>125/4
n>31.25
Therefore, the first negative term of the series is 32nd term.
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