Question

which term of AP 121 117 113 is its first negative term

Answer 1

here is the solution.

Answer 2

Given:first term(a)= 121 
common difference (d)= 117- 121 = -4
∵ n th term of an AP

an = a + (n – 1)d
⇒121+(n-1) ×(-4)
⇒121-4n+4
⇒12+4-4n
⇒125 -4n
an= 125 -4n

For first negative term , an <0
⇒ 125-4n<0
⇒125<4n
⇒4n>125
⇒n>125/4
⇒n> 31 1/4

least integral value of n= 32

Hence, 32nd term of the given AP is the first negative term. 

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