What "i" can be simplified to - 1

When "i" is raised to a power divisible by 4, it can be simplified to 1 (i^4, i^64, etc.)

When "i" is raised to a power divisible by 3, it can be simplified to - i (i^3, i^27, etc.)

When "i" is raised to a power divisible by 2 but not 4, it can be simplified to - 1 (i^2, i^10, etc.)

When none of this is true for the power "i" is being raised to, then it can be simplified to "i" (i^5, i^11, etc.)

I=√-1

i² = (√-1) ²=-1

the answer is i²