$解：??(1)??將點(diǎn)??B(2，????-4)??代入反比例函數(shù)得，??-4=\frac m 2，????m=-8??$
$?? ∴y=-\frac 8x??$
$ 令??x=-4，????n=-\frac 8{-4}=2??$
$ 將點(diǎn)??A(-4，????2)、????B(2，????-4)??代入一次函數(shù)表達(dá)式得??\begin{cases}-4k+b=2\\2k+b=-4\end{cases} ??$
$?? ∴y=-x-2??$
$?? (2)??令??y=0，????-x-2=0，????x=-2??$
$?? ∴C(-2，????0)??$
$?? S_{△AOB}=\frac 12×6×6-\frac 12×6×2-\frac 12×6×2=6??$
$?? (3)??由圖可知，??-4＜x＜0??或??x＞2??$
