Function int_kw_popr(zakres_X As Range, zakres_Y As Range, x0) As Single
Dim x2w(1 To 3, 1 To 3) As Single
Dim x(1 To 3) As Single
Dim y(1 To 3) As Single
Dim i As Integer, n As Integer, j As Integer
Dim bmin As Single
n = zakres_X.Cells.Count
bmin = WorksheetFunction.Large(zakres_X, 1) + WorksheetFunction.Large(zakres_X, 2) + WorksheetFunction.Large(zakres_X, 3)
For i = 1 To n - 2
    If Abs(zakres_X.Cells(i) + zakres_X.Cells(i + 1) + zakres_X.Cells(i + 2) - 3 * x0) < bmin Then
        bmin = Abs(zakres_X.Cells(i) + zakres_X.Cells(i + 1) + zakres_X.Cells(i + 2) - 3 * x0)
        j = i
    End If
Next i
For i = 1 To 3
    x(i) = zakres_X.Cells(j + i - 1): y(i) = zakres_Y.Cells(j + i - 1)
Next i
x2w(1, 1) = 1: x2w(2, 1) = 1: x2w(3, 1) = 1 'tworzenie macierzy 3x3
x2w(1, 2) = x(1): x2w(2, 2) = x(2): x2w(3, 2) = x(3)
x2w(1, 3) = x(1) ^ 2: x2w(2, 3) = x(2) ^ 2: x2w(3, 3) = x(3) ^ 2
A = WorksheetFunction.MMult(WorksheetFunction.MInverse(x2w), WorksheetFunction.Transpose(y))
int_kw_popr = A(1, 1) + A(2, 1) * x0 + A(3, 1) * x0 * x0
End Function