both i and -i being roots does not imply they are equal.
look at x^2 - 1 = 0
the roots are 1 and -1, does that mean 1 = -1? of course not
CaptainBlack called both x, but he was suggesting that these are the x-values that give roots for the equation, not that they are equal. an abuse of notation, i know, but it is understood in the context
complex roots come in conjugate pairs. we get complex roots when we take even roots of negative numbers, these roots therefore come in +/- form