Answer
$\frac{2\pm\sqrt {6}}{2}$
Work Step by Step
Let $f(x)=0$, we have $-2x^2+4x+1=0 \Longrightarrow x=\frac{-4\pm\sqrt {16-4(-2)}}{2(-2)}=\frac{2\pm\sqrt {6}}{2}$
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