Question

find the no. of the terms of A.P 30,28,26... so that their sum is zero.​

Answer 1

Let first term be a=27

And common difference be d=−3

According to question, sum is zero,

n/2[2a+(n−1)d]=0

[54+(n−1)(−3)]=0

n=19

Hence, 19 terms of AP should be taken to make sum zero.

Value of the last term

a19=a+(19−1)d

a19=27+(18)(−3)

a19=-27