Ta có 3x²-x-2 =0
⇔3x²-3x+2x-2 =0
⇔3x(x-1)+2(x-1)=0
⇔(3x+2)(x-1)=0
⇔\(\left[ \begin{array}{l}3x+2=0\\x-1=0\end{array} \right.\)
⇔\(\left[ \begin{array}{l}x=-2/3\\x=1\end{array} \right.\)
M= $\frac{-2}{3}$( $\frac{-2}{3}$-2)+1(1-2) =$\frac{7}{9}$
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