Is -i9 a real number

Answer 1

If you mean i9, or -i9, or even (-i)9, no - it isn't. The powers of i are:

i, -1, -i, 1, i, -1, -i, 1, ...

Whereas the powers of (-i) are:

-i, -1, i, 1, -i, -1, i, 1, ...

The pattern repeats in both cases. In other words, all even powers of i (or of (-i)) are real numbers; all odd powers are pure imaginary numbers.