Dim x1, x2, xa, xb
x1 = -2: x2 = -1: x = -1.5
Do Until Abs(x ^ 6 - 5 * x ^ 5 + 3 * x ^ 4 + x ^ 3 - 7 * x ^ 2 + 7 * x - 20) < 0.00001
If x ^ 6 - 5 * x ^ 5 + 3 * x ^ 4 + x ^ 3 - 7 * x ^ 2 + 7 * x - 20 > 0 Then
x1 = x: x = (x1 + x2) / 2
Else
x2 = x: x = (x1 + x2) / 2
End If
Loop
xa = x
x1 = 4: x2 = 5: x = 4.5
Do Until Abs(x ^ 6 - 5 * x ^ 5 + 3 * x ^ 4 + x ^ 3 - 7 * x ^ 2 + 7 * x - 20) < 0.00001
If x ^ 6 - 5 * x ^ 5 + 3 * x ^ 4 + x ^ 3 - 7 * x ^ 2 + 7 * x - 20 < 0 Then
x1 = x: x = (x1 + x2) / 2
Else
x2 = x: x = (x1 + x2) / 2
End If
Loop
xb = x
MsgBox "該方程在-2，5區間的兩個零點的近似值分別是" & xa & "和" & xb
End Sub
Private Sub Form_Load()
Me.AutoRedraw = True
Me.Width = 8000
Me.Height = 8200
Me.Scale (-6, 400)-(6, -400)
'x^6-5*x^5+3*x^4+x^3-7*x^2+7*x-20=0
Line (-6, 0)-(6, 0)
Line (0, 400)-(0, -400)
For i = -5 To 5
Line (i, 20)-(i, 0)
CurrentX = CurrentX - 0.3
Print i
Next i
For x = -2 To 5 Step 0.001
j = x ^ 6 - 5 * x ^ 5 + 3 * x ^ 4 + x ^ 3 - 7 * x ^ 2 + 7 * x - 20
PSet (x, j)
Next x
End Sub