The question is given from NCERT Book of class 10th Ch. no. 5 Ex. 5.2 Q. 8. In the following question you have to find which term in this series will be zero if 3rd term is 4 & 9th term is -8.

Deepak BoraNewbie

# If the 3rd and 9th terms of an A.P. are 4 and − 8 respectively. Which term in this A.P. is zero.

Share

Solution:3rd term, a

_{3}= 1250th term, a

_{50}= 106We know,

a=_{n}a+(n−1)da_{3}=a+(3−1)d12 =

a+ 2d…………………………….(i)Like this,

a_{50 }=a+ (50−1)d106 =

a+ 49d………………………….(ii)By subtracting

(i)from(ii),94 = 47

dd= 2From equation

(i),12 =

a+ 2(2)a= 12 − 4 = 8a_{29}=a+ (29−1)da_{29}= 8 + (28)2a_{29}= 8 + 56 = 64The 29th term of the give A.P is 64.