11.研1忒対121, 117, 113,韌积 Της TTT RuirTF Rem ?Which term of

1.	11.研1忒対121, 117, 113,韌积 Της TTT RuirTF Rem ?Which term of the A.P.: 121, 117, 113,.. .is its first negative term ?
Answer» Given:first term(a)= 121common 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 -4nan= 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.

11.研1忒対121, 117, 113,韌积 Της TTT RuirTF Rem ?Which term of the A.P.: 121, 117, 113,.. .is its first negative term ?

Answer»

Given:first term(a)= 121common 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 -4nan= 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.