急求高手帮我解决一道VB编程题 关于速度时间曲线的 已知一点的速度 求速度时间曲线

Private Function jiecheng(x As Integer) As Long '定义阶乘函数
jiecheng = 1
For i = 1 To x
jiecheng = jiecheng * i
Next i
End Function
Private Sub Command1_Click() 'sub求阶乘
a =