在vb中使用图表的不均匀抛物线？

Question

我对视觉基础很新。我的程序让你输入参数（a，b，c，xmin，xmax，ymin，ymax和数据点数）来绘制抛物线。当输入更多数据点时，抛物线看起来很好。问题是如果有4个数据点，则抛物线不均匀2个点。我真的很难找到解决方案，所以任何指导都会非常感激。

这是我的代码：

Public Sub FillGraph()
    myChart.Series(0).Points.Clear()
    myChart.Series(0).ChartType = _
        DataVisualization.Charting.SeriesChartType.Line

    If IsNumeric(txtxMax.Text) And IsNumeric(txtxMin.Text) And IsNumeric(txtyMax.Text) And IsNumeric(txtyMin.Text) Then
        ymin = CDbl(txtyMin.Text)
        ymax = CDbl(txtyMax.Text)
        xmax = CDbl(txtxMax.Text)
        xmin = CDbl(txtxMin.Text)
        dataPts = CDbl(txtDataPts.Text)


        a = CInt(txtA.Text)
        b = CInt(txtB.Text)
        c = CInt(txtC.Text)
        Dim x As Integer
        For x = CInt((-dataPts / 2)) To CInt(dataPts / 2)
            myChart.ChartAreas(0).Axes(0).Maximum = xmax
            myChart.ChartAreas(0).Axes(0).Minimum = xmin
            myChart.ChartAreas(0).Axes(1).Maximum = ymax
            myChart.ChartAreas(0).Axes(1).Minimum = ymin
            myChart.Series(0).Points.AddXY(x, (a * (x ^ 2)) + (b * x) + c)
        Next
    End If
End Sub
Private Sub TabControl1_SelectedIndexChanged(sender As Object, e As EventArgs) Handles TabCtrl.SelectedIndexChanged
    If TabCtrl.SelectedIndex = 2 Then
        Call FillGraph()
        Call FillLbls()
    End If
End Sub
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
    myChart.Series(0).Color = Color.Red
    myChart.Series(0).BorderWidth = 5

End Sub