Problem:
If i2=−1, then (i−i−1)−1=
Answer Choices:
A. 0
B. −2i
C. 2i
D. −i/2
E. i/2
Solution:
(i−i−1)−1=(i−i1​)−1=(ii2−1​)−1=(i−2​)−1=−2i​
OR
Since i−1=−i, it follows that
(i−i−1)−1=(i−(−i))−1=(2i)−1=2i1​=−2i​