vb代碼如下：
Private Sub Command1_Click()
Dim a As Single, b As Single, c As Single
Dim d As Single, x1 As Single, x2 As Single
a = InputBox("請輸入一元二次方程的系數(shù)a")
b = InputBox("請輸入一元二次方程的系數(shù)b")
c = InputBox("請輸入一元二次方程的系數(shù)c")
If a = 0 Then
a = InputBox("因?yàn)閍≠0,你輸入的a＝0,請重新輸入系數(shù)a")
End If
d = b * b - 4 * a * c
If d >= 0 Then
x1 = (-b + Sqr(d)) / (2 * a)
x2 = (-b - Sqr(d)) / (2 * a)
Print "系數(shù)為"; a; b; c; "的一元二次方程的根分別為"; x1
Print "系數(shù)為"; a; b; c; "的一元二次方程的根分別為"; x2
Else
Print "此方程在實(shí)數(shù)范圍內(nèi)無解"
End If
End Sub
一、按鈕“求一元二次方程”的vb代碼如下：
Private Sub Command1_Click()
a = Text1.Text
b = Text2.Text
c = Text3.Text
d = b * b - 4 * a * c
If d >= 0 Then
X1 = (-b + Sqr(d)) / (2 * a)
X2 = (-b - Sqr(d)) / (2 * a)
Label4.Caption = X1
Label5.Caption = X2
Else
Label4.Caption = "在實(shí)數(shù)范圍內(nèi)無解"
End If
End Sub
二、按鈕“重置”的vb代碼如下：
Private Sub Command2_Click()
Text1.Text = ""
Text2.Text = ""
Text3.Text = ""
Label4.Caption = ""
Label5.Caption = ""
End Sub
三、按鈕“退出”的vb代碼如下：
Private Sub Command3_Click()
End
End Sub
特殊例子（指定系數(shù)c的值為5）：
在窗體“Form1.frm”的“Command1_click“事件中編寫代碼（請不要隨便更改其它代碼）,使之能夠?qū)崿F(xiàn)如下功能：在Text1輸入整數(shù)a、、Text2輸入b,判斷一元二次方程ax2+bx+5=0有無實(shí)數(shù)根.并在Text3文本框中顯示判斷結(jié)果,即有實(shí)數(shù)根則在Text3文本框中輸出“有”,否則輸出“無”.
VB程序代碼如下：
Private Sub Command1_Click()
dim a as single,b as single
a = Text1.Text
b = Text2.Text
d = b * b - 4 * a * 5
If d >= 0 Then
Text3.Text="有"
Else
Text3.Text="無"
End If
End Sub
如果不用dim定義變量,則上面的輸入部分語句改為下面的語句,這樣可以把字符變量類型轉(zhuǎn)化為數(shù)值類型：
a =val(Text1.Text)
b =val(Text2.Text)
樓主.給你寫這么呢多你不給加點(diǎn)分嗎?= =||