Help me with math

Question

I don't understand the whole i=root -1 thingy!!help

Answer 1

It is a definition! i = sqrt(-1)

Now look at this pattern: [sqrt(3)]² = 3, [sqrt(16)]² 16, [sqrt(5)]² = 5.

So [sqrt(-1)]² = -1

Now i³ = i²*i =(-1)i = -i

Now i⁴ = i²*i² = (-1)(-1) =1