Expert Answers
lemjay eNotes educator| Certified Educator

To take the sum of -i and i, the operation that should be performed is addition.

`-i + i`

To add like terms,  add the coefficients and copy the variable. Since there are no written numbers at the side of -i and i, it indicates that the coefficients are -1 and 1, respectively.

`= -1i + 1i`





Therefore,  the sum of -i and i is zero.

`-i + i = 0`