Question

how many terms of the AP 21 18 15 must be added to get the sum of zero

Answer 1

let n be no of terms

As common difference ( D) = -3

So Sum = n/2 ( 2×21 + ( n-1)× -3))

0 = 42 -3n +3

45 = 3n

n= 15

So total 15 terms

Answer 2

Refers to attachment ♡~