B
baby_1995
dựa vào viet ta có
{xM+xN=−mxM.xN=2m−1
[TEX] I x_M - x_N I = 1[/TEX]
=> [TEX](x_M - x_N)^2 = 1[/TEX]
<=> [TEX](x_M + x_N)^2 - 4x_Mx_N =1[/TEX]
<=> [TEX](-m)^2 - 4. \frac{m - 1}{2} = 1[/TEX]<=> m^2 - 2m + 1 = 0
<=> [TEX](m - 1)^2 = 0[/TEX]
<=> [TEX]m- 1 = 0[/TEX]
<=> [TEX]m = 1[/TEX]
vậy ................................
{xM+xN=−mxM.xN=2m−1
[TEX] I x_M - x_N I = 1[/TEX]
=> [TEX](x_M - x_N)^2 = 1[/TEX]
<=> [TEX](x_M + x_N)^2 - 4x_Mx_N =1[/TEX]
<=> [TEX](-m)^2 - 4. \frac{m - 1}{2} = 1[/TEX]<=> m^2 - 2m + 1 = 0
<=> [TEX](m - 1)^2 = 0[/TEX]
<=> [TEX]m- 1 = 0[/TEX]
<=> [TEX]m = 1[/TEX]
vậy ................................