Question

-4+4-4+ 4-_ _ _ _ _ _ _-4 (21times)

Answer 1

ans will be 4 or -4 chances if we count from 4 then ans will be 4 and if count from -4 ans is -4. rest all zero.

Answer 2

answer is -4 because all even term zero i.e to 20th term it make zero & then remain-4 so answer is-4