\psaxes{->}(0,0)(-2,0)(2,4)
\psset{linewidth=2\pslinewidth}
\psplot[linecolor=gray]{-2}{2}{x 2 exp}
\psplot{-2}{2}{2 x 2 div sub}
\psset{PointSymbol=o}
\pstInterFF{2 x 2 div sub}{x 2 exp}{1}{M_1}
\pstInterFF{2 x 2 div sub}{x 2 exp}{-2}{M_0}
