Question

sn =0,a= 18,d=-2,n=?​

Answer 1

ANSWER

In AP , given that a=−2 and d=4

Given that the sum of first n terms in the series is S n =160

We know that the sum of first n terms in the series is S n = 2n

(2a+(n−1)d)⇒ 2n

(2a+(n−1)d)=160⇒ 2n

(−4+4(n−1))=160

⇒n(n−2)=80

⇒n=10,−8

Since n is positive integer , the value of n=1

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