怎么用VB来求Y=1-1/2+1/3-1/4+1/5-1…前30项之和。

怎么用VB来求Y=1-1/2+1/3-1/4+1/5-1…前30项之和。

Private Sub Command1_Click()
Dim sum1 As Long
Dim a, i, j As Integer
sum = 0
j = 1
For i = 1 To 30
sum = sum + j * 1 / i
j = j * -1
Next i
MsgBox sum
End Sub

For i = 1 To 30 If i Mod 2 = 0 Then s = s - 1 / i Else s = s + 1 / i End If Next i Print s

Private Sub Form_Load() MsgBox Sum(30) End Sub Function Sum(ByVal n As Integer) As Single

Dim i As Integer Sum = 0 For i = 1 To 30 Sum = Sum + (-1) ^ (i + 1) * (1 / i) Next End Function

for i = 1 to 30

sum = sum+(-1)^(i+1)*1/i

next i

msgbox sum

Option Explicit Const N = 30 '30项 Private Sub Form_Activate() Dim i As Integer, s For i = 1 To N s = s + (-1) ^ (i - 1) / i Next MsgBox N & "项之和：" & Format(s, "0.00000000") Unload Me End Sub

Private Sub Command1_Click() Dim i As Integer Dim j As Integer Dim s As Single j = -1 For i = 1 To 30 j = -1 * j s = s + j * 1 / i Next Print s End Sub