Question

·VB用迭代法求立方根

用迭代法求x=a^(1/3),求立方根的迭代公式为：xi+1=2/3xi+a/3xi*xi
迭代到xi+1-xi的绝对值小于十的负五为止，xi+1为方程的近似值，显示a=3,27的值，并通过求a^(1/3)的表达式加以验证
急啊急啊急啊急啊急啊急啊

Answer 1

Dim x1&, x0&, t!
Private Sub Command1_Click()
x0 = Val(Text1)
a=x0
Do
x1 = (2 / 3) * x0 + (a / (3 * x0*x0))
t = x0
x0 = x1
Loop Until Abs(x0 - t) < 10 ^ (-5)
Text2 = x1
End Sub

以上为用迭代法求立方根的代码。
期待被采纳!

Answer 2

Option Explicit
Private Sub Command1_Click()
Dim a&, b!, c!
a = 3
b = a
Do
c = 2 * b / 3 + a / (3 * b * b)
If Math.Abs(b - c) < 0.00001 Then Exit Do
b = c
Loop
Text1.Text = a & "立方根为：" & c & vbCrLf & "利用运算符求得3的立方根为：" & a ^ (1 / 3)
a = 27
b = a
Do
c = 2 * b / 3 + a / (3 * b * b)
If Math.Abs(b - c) < 0.00001 Then Exit Do
b = c
Loop
Text2.Text = a & "立方根为：" & c & vbCrLf & "利用运算符求得3的立方根为：" & a ^ (1 / 3)
End Sub