求解二次函数的程序vb

Private Sub Command1_Click()
a = Val(InputBox("“a=”"))
b = Val(InputBox("“b=”"))
c = Val(InputBox("“c=”"))
D = b ^ 2 - 4 * a * c
If a = 0 Then
MsgBox " “a” 不能等于零"
ElseIf D > 0 Then
P = -b / (2 * a)
X1 = P + Sqr(D) / (2 * a)
X2 = P - Sqr(D) / (2 * a)
MsgBox "x1 =" + Str(X1) + " ," + "x2 =" + Str(X2), , "二次方程的两根"
ElseIf D = 0 Then
P = -b / (2 * a)
MsgBox "x1 =" + "x2 =" + Str(P), , "二次方程的两根"
ElseIf b = 0 Then
e = -b / (2 * a)
f = Sqr(-D) / (2 * a)
MsgBox "x1=" + "x2=" + Str(f) + "i", , "二次方程的两根"
Else
e = -b / (2 * a)
f = Sqr(-D) / (2 * a)
MsgBox "x1=" + Str(e) + "+" + Str(f) + "i" + ", " + "x2=" + Str(e) + "-" + Str(f) + "i", , "二次方程的两根"
End If
End Sub

通用段：Dim a As Single, b As Single, c As Single, X1 As Double, X2 As Double, T As DoublePrivate Sub Command1_Click()InputBox "请输入a的值"
InputBox "请输入b的值"
InputBox "请输入c的值"T = b ^ 2 - 4 * a * c
If T < 0 Then
MsgBox ("该方程无实数根")
Else
X1 = (-b + Sqr(b ^ 2 - 4 * a * c)) / (2 * a)
X2 = (-b - Sqr(b ^ 2 - 4 * a * c)) / (2 * a)MsgBox ("方程的解是：" & X1 & "和" & X2)End If
End Sub