3道VB编程题~急

来源：百度知道 编辑：UC知道 时间：2024/05/17 22:12:47
1 用文本框输入n值，单击某命令按钮求以下S值，用文本框显示结果
S=4*（1-1/3+1/5-1/7+1/9-…+(-1)^n+1*1/(2n-1)）

2 求Sn=a+aa+aaa+…+a…a {n个a} 的值 例：2+22+222+2222=S4 {此时n=4} n和a由输入框输入

3 分数序列2/1，3/2，5/3，8/5，… 单击窗体求该数列前20项和，用消息框显示结果

先谢过各位电脑达人了！~~

1.
Dim N As Long
Dim S As Single
Private Sub Command1_Click()
N = Val(InputBox("请输入N", "请求数据"))
For i = 1 To 2 * N - 1 Step 2
S = S + (-1) ^ N + 1 / (2 * N - 1)
Next i
Me.Print S
End Sub
Private Sub Form_Load()
S = 0
N = 0
End Sub

2.
Dim A As Long, N As Long
Dim Sn1 As Long, Sn As Long
N = Int(Val(InputBox("请输入N", "请求数据")))
A = Int(Val(InputBox("请输入a", "请求数据")))
For i = 1 To N
Sn1 = 0
For j = 1 To i
Sn1 = Sn1 + A * 10 ^ (j - 1)
Next j
Sn = Sn + Sn1
Next i
Me.Print Sn
3。
Dim A As Long, B As Long
Dim s As Single
A = 1: B = 2
For i = 1 To 20
s = s + A / B
A = A + B: B = A
Next i
Me.Print s

数字不要太大！会超范围的！没写数字判断！自己看吧~~

1、
Private Sub Command1_Click()
Dim n As Single, sum As Single
n =