Question

VB程序设计习题代码

计算表达式
S=1-2/x+3/x^2-4/x^3+……，x>1
要求计算精度为第n项绝对值小于10^(-5)
怎么搞？？
写不出来啊。。运行程序一直显示0。。。。
求指教~~

Answer 1

Private Sub Command1_Click()
Dim sum As Double, i As Integer
Dim b(1000) As Single
Dim x As Single
b(0) = 1
x = InputBox("请输入大于1的数字：", "数据输入")
If x <= 1 Then
MsgBox ("X值输入错误！请输入大于1的数字！")
End If
For i = 1 To 1000 ' 从第二项开始赋值
b(i) = (-1) ^ i * (i + 1) / x ^ i
If Abs(b(i)) > 10 ^ (-5) Then
sum = sum + b(i)
Else
Exit For
End If
Next i
Print Format(sum, "0.00000000000000")
Print "从第" & i + 1 & "项开始小于10^(-5)"
End Sub

Answer 2

Private Sub Form_Click()
Dim i%, n&, t!, s!
s = 0
x = 3 ‘假设x的值为3
n = 1
t = 1
Do While Abs(t) > 0.00001
If i Mod 2 Then
s = s + t
Else
s = s - t
End If
n = n + 1
t = n / (x ^ (n - 1))
Loop
Print s
End Sub

Answer 3

Private Sub Command1_Click()
Print sum(2!)
End Sub
Function sum!(x!)
Dim i&, j!
sum = 1
j = 1
i = 1
Do While Abs(j) > 0.00001
j = j / i
i = i + 1
j = -j * i / x
sum = sum + j
Loop
End Function