why is root 3i multiplied by - root 3i equal to 3? √3i x (-√3i) = 3
$$i=\sqrt{-1}$$ It is an imaginary number.
$$i\times i = \sqrt{-1}\times \sqrt{-1} = -1$$
SO
√3i x (-√3i)
$$\\=\sqrt3\times i\times -\sqrt3\times i\\ =-\sqrt3\times\sqrt3\times i\times i\\ =-\sqrt9\times i\times i\\ =-3\times -1\\ =3$$