Public Function factor(a, b, c)
    answerString = ""
    needNegativeSign = False
    If a < 0 Then
        needNegativeSign = True
        a = a*(-1)
        b = b*(-1)
        c = c*(-1)
    End If
    product = Abs(a * c)
    If c = 0 Then
        n = gcf(Abs(a), Abs(b))
        answerString = n & "*x*(" & (a / n) & "*x + " & (b / n) & ")"
        answerString = Replace(answerString, "+ -", "- ")
    Else
        For i = 1 to int(sqr(product))
            If product Mod i = 0 Then
                n1 = i
                n2 = product / i
                If c < 0 Then
                    If n1 - n2 = b Then
                        GCF1 = gcf(a, n1)
                        GCF2 = gcf(n2, c)
                        answerString = "(" & GCF1 & "*x - " & GCF2 & ")*(" & (a / GCF1) & "*x + " & (n1 / GCF1) & ")"
                        Exit For
                    ElseIf n2 - n1 = b Then
                        GCF1 = gcf(a, n1)
                        GCF2 = gcf(n2, c)
                        answerString = "(" & GCF1 & "*x + " & GCF2 & ")*(" & (a / GCF1) & "*x - " & (n1 / GCF1) & ")"
                        Exit For
                    End If
                Else
                    If n1 + n2 = b Or n1 + n2 = -b Then
                        GCF1 = gcf(a, n1)
                        GCF2 = gcf(n2, c)
                        answerString = "(" & GCF1 & "*x + " & GCF2 & ")*(" & (a / GCF1) & "*x + " & (n1 / GCF1) & ")"
                        If n1 + n2 = -b Then
                            answerString = Replace(answerString, "+", "-")
                        End If
                        Exit For
                    End If
                End If
            End If
        Next
    End If
    If answerString <> "" Then
        answerString = replace(answerString, "(-1*", "(")
        answerString = replace(answerString, "(1*", "(")
        answerString = replace(answerString, "*", "")
        If needNegativeSign Then
            answerString = "-" + answerString
        End If
        factor = answerString
    Else
        factor = "cannot factor"
    End If
End Function