vb 一元二次方程

Question

Private Sub Command1_Click()
Dim a!, b!, c!, x1!, x2!, disc!
a = Val(Text1)
b = Val(Text4)
c = Val(Text3)
disc = b * b - 4 * a * c
If Text1 < -20 Or Text1 > 20 Or Text4 < -20 Or Text4 > 20 Or Text3 < -20 Or Text3 > 20 Then
MsgBox "超出范围 请在0-20内输入", 2 + vbExclamation, "错误提示"
Else
If a = 0 Then
x = Text3 / -Text4
Text2.Visible = False
Text5.Visible = False
Label6.Visible = False
Label7.Visible = False
Label3.Visible = True
Text6.Visible = True
Label1.Visible = True
Label8.Visible = False
Text6.Text = Str$(x)
Else
If disc > 0 Then
x1 = (-b + Sqr(disc)) / (2 * a)
x2 = (-b - Sqr(disc)) / (2 * a)
Label1.Visible = True
Label8.Visible = False
Label7.Visible = True
Label6.Visible = True
Text5.Visible = True
Text2.Visible = True
Text2.Text = Str$(x1)
Text5.Text = Str$(x2)
ElseIf disc = 0 Then
x = (-b) / (2 * a)
Text2.Visible = False
Text5.Visible = False
Label6.Visible = False
Label7.Visible = False
Label3.Visible = True
Text6.Visible = True
Label1.Visible = True
Label8.Visible = False
Text6.Text = Str$(x)
Else
Label8.Visible = True
End If
End If
End If
End Sub

Private Sub Command2_Click()
Text1 = ""
Text2 = ""
Text2 = ""
Text3 = ""
Text4 = ""
Text5 = ""
Label8.Visible = False
Label7.Visible = False
Label6.Visible = False
Label1.Visible = False
Text2.Visible = False
Text5.Visible = False
Label3.Visible = False
Text6.Visible = False
End Sub

Private Sub Form_Load()
Label6.Visible = False
Text2.Visible = False
Label3.Visible = False
Text6.Visible = False
Label1.Visible = False
Label7.Visible = False
Text5.Visible = False
Label8.Visible = False
End Sub
这个算出来的答案怎么老是不对？
高手们帮忙解决哈！谢谢

Answer 1

原代码有如下几个地方需要注意：
1、text是个控件，默认text的值是字符串形式的，如果要和数值比较，要将它转换为数值。都用val函数转换了，比较时就该用转换后的值。
2、msgbox既可以做语句，也可以做函数，如果让它有“终止”、“重试”、“忽略”三个按钮，那么，要针对这三个按钮分别做一下处理。否则，不如默认它只有“确定”一个按钮。
3、考虑到a＝0，但没考虑到b＝0，原代码中有b做除数的情况，这时候一定要把b=0的情况排除掉，不然会出错。既然要全面考虑，那就应该考虑到各种情况。

Command1_Click()的代码如下（Command2和Form的事件过程没做改动）：
Private Sub Command1_Click()
Dim a!, b!, c!, x1!, x2!, disc!, f%
Dim flag As Boolean
a = Val(Trim(Text1))
b = Val(Trim(Text4))
c = Val(Trim(Text3))
flag = True
If a < -20 Or a > 20 Or b < -20 Or b > 20 Or c < -20 Or c > 20 Then
f = MsgBox("超出范围 请在0-20内输入", 2 + vbExclamation, "错误提示")
If f = 3 Then flag = False '选择“终止”，则什么都不做
If f = 4 Then '选择“重试”，则将不符合要求的输入清空
If a < -20 Or a > 20 Then Text1.Text = ""
If b < -20 Or b > 20 Then Text4.Text = ""
If c < -20 Or c > 20 Then Text3.Text = ""
flag = False
End If
If f = 5 Then flag = True '选择“忽略”，则继续运行
End If
disc = b * b - 4 * a * c
If flag = True Then
If a = 0 Then
Text2.Visible = False
Text5.Visible = False
Label6.Visible = False
Label7.Visible = False
Label3.Visible = True
Text6.Visible = True
Label1.Visible = True
Label8.Visible = False
If b = 0 And c = 0 Then
Text6.Text = "解为任意数"
ElseIf b = 0 And c <> 0 Then
Text6.Text = "无解"
Else '即a=0且b<>0且c<>0的情况
x = Format(-c / b, ".00")
Text6.Text = x
End If
Else
If disc > 0 Then
Label1.Visible = True
Label8.Visible = False
Label7.Visible = True
Label6.Visible = True
Text5.Visible = True
Text2.Visible = True
x1 = Format((-b + Sqr(disc)) / (2 * a), ".00")
x2 = Format((-b - Sqr(disc)) / (2 * a), ".00")
Text2.Text = x1
Text5.Text = x2
ElseIf disc = 0 Then
Text2.Visible = False
Text5.Visible = False
Label6.Visible = False
Label7.Visible = False
Label3.Visible = True
Text6.Visible = True
Label1.Visible = True
Label8.Visible = False
x = Format((-b) / (2 * a), ".00")
Text6.Text = x
Else
Text6.Text = "无解"
Label8.Visible = True
End If
End If
End If
End Sub

Answer 2

你算什麽啊..什麽乱七八糟的代码

Answer 3

Private Sub Command1_Click()
If a <> 0 And b^2 - 4 * a * c <0 Then
Text4 = (-b) / (2 * a) & "+j" & Sqr(-b ^ 2 + 4 * a * c) / (2 * a)
Text5 = (-b) / (2 * a) & "-j" & Sqr(-b ^ 2 + 4 * a * c) / (2 * a)
End If
End Sub

全部：
Dim a, b, c As Integer

Private Sub Command1_Click()
a = Val(Text1)
b = Val(Text2)
c = Val(Text3)
If a = 0 Then
MsgBox "这是一元一次方程"
x = -c / b
Text4.Visible = False
Text5 = x
Else
If a <> 0 And (b * b) - 4 * a * c >= 0 Then
Text4.Text = Val((-b + Sqr((b * b) - 4 * a * c)) / 2 * a)
Text5.Text = Val((-b - Sqr((b * b) - 4 * a * c)) / 2 * a)
ElseIf a <> 0 And (b * b) - 4 * a * c < 0 Then
Text4 = (-b) / (2 * a) & "+j" & Sqr(-b ^ 2 + 4 * a * c) / (2 * a)
Text5 = (-b) / (2 * a) & "-j" & Sqr(-b ^ 2 + 4 * a * c) / (2 * a)
End If
End If
End Sub

Private Sub Text1_Click()
Text1 = InputBox("请输入数值", "输入框")
End Sub

Private Sub Text2_Click()
Text2 = InputBox("请输入数值", "输入框")
End Sub

Private Sub Text3_Click()
Text3 = InputBox("请输入数值", "输入框")