为什么我一运行结果就是（1+4）/2=2.5   根本不循环？？？？
Private Sub Form_Load()

    Dim l As Double, u As Double, m As Double
   
    l = 1
    u = 4
    f = x ^ 3 + 4 * x ^ 2 - 10
     m = (u + l) / 2
            
    Do While (u - l) > 0.001
   
        
        If fm * fl = 0 Then Exit Do
        If fm * fl > 0 Then
            l = m
           
        Else
            u = m

        End If
    Loop
    MsgBox "x=" & m
End Sub

求的是x ^ 3 + 4 * x ^ 2 - 10 在（1，4）的近似根