用二分法求函数 f(x)=x3-6x-1=0 在 x=2 ~ 5 范围内的 x=2 附近的一个实根,其计算误差为 | x1-x2|<10^-6 。请将下列程序补充完整。 Private Sub Command1_Click() Dim v0 As Single, v As Single, S As String Dim X As Single, t As Single, x1 As Single, x2 As Single X1=2: x2=5 Do While ________________ X=(x1+x2) / 2 If Sgn(x*x*x-6*x-1)=1 Then x2=x Else x1=x End If Loop Print "x="; x End Sub