Question

how many term of 20,18,16..... are needed give sum zero

Answer 1

Let an be 0,
an = a + (n-1)d
0 = 20 + (n-1)(-2)
0 = 20 - 2n + 2
0 = 22 - 2n
2n = 22
n = 11

Hence, 11th term would be 0.
Hope, this will help you, mate!!

Answer 2

i hope this may help you