Question

how many terms of ap21,18,15.... must be added to get the sum of 0
plz help me give correct answer plz my friends​

Answer 1

Answer:

15.

Step-by-step explanation:

a = 21.

d = –3.

Sum = 0

(n/2)[2a+(n-1)d] = 0

n[2(21)+(n-1)(-3)] =0

n[42-3n+3] = 0

n[ 45-3n] = 0.

n=0{NOT POSSIBLE}.

45-3n =0.

3n = 45

n= 15.