Question

Why is 2i * -2i equal to 4, and not -4i?

Answer 1

The answer is 4 (working below), It is not
`-4i` because
`i * i = i^2`.

Explanation:

`2i * -2i`

Multiply.

`2 * i * -2 * i`

`-4i^2`

Apply :
`i^2 = -1`

`-4(-1)`

`=4`

Answer 2

see below

Explanation:

2i * -2i = -4 i^2

We know that i^2 = -1

= -4 * -1

= 4

It is not equal to -4i because we need to multiply i*i which is i^2 not i