đây là bài làm của bạn NGHĨA
Function KtraSNT(ByVal N As Long) As Boolean
Dim i As Long
ktraSNT=true
If (N < 2) Then
KtraSNT = False
Else
i = 2
kq = True
Do While (i < N) And (ktraSNT = True)
If (N Mod i = 0) Then ktraSNT = False
i = i + 1
Loop
End If
End Function
_____________________________________________________________________________
Private Sub Command4_Click()
Dim a, b, i As Long
a = CLng(Val(txtfrom.Text))
b = CLng(Val(txtto.Text))
For i = a To b
If (KtraSNT(i) = True) Then
txtkq.Text = txtkq.Text & i & " "
End If
Next
End Sub
