In a answered math the problem √(-2) plus √(-18) was 4√(2i) as it was rewritten as √(2i) + √(18i). Why can √(-2) be written as√(2i)

Question

In a answered math the problem
`√(-2)` plus
`√(-18)` was
`4√(2i)` as it was rewritten as
`√(2i) + √(18i)`. Why can
`√(-2)` be written as
`√(2i)`

Answer 1

Ok so basically this is this and that is that !

Answer 2

`\text{The imaginary unit,}~ i = √(-1)\\\\√(-2) ~ \text{can be written as.}\\\\√(-2)\\\\=√(-1 \cdot 2)\\\\=√(-1) √(2)\\\\=i\sqrt 2\\\\=\sqrt 2 i`