Đáp án:
$\rm b)\text{PT có 2 nghiệm x1,x2}\\\to \Delta \geq 0\\\to 4m^2-4m+1-4m^2+8 \geq 0\\\to -4m \geq -9\\\to m \leq \dfrac{9}{4}\\\text{Áp dụng viets:}\\x_1+x_2=2m-1,x_1.x_2=m^2-2\\x_1.x_2=2(x_1+x_2)\\↔m^2-2=2(2m-1)\\↔m^2-4m=0\\↔↔\left[ \begin{array}{l}m=0\\m=4(l)\end{array} \right.\,\,thì\,\,pt\,\,có\,\,2\,\,nghiệm\,\,thỏa\,\,mãn:2(x_1+x_2)=x_1.x_2$
