Найти экстремальное значение ф-ии при изменение аргумента от Х нач. до Х кон. с шагом Н ф-ия : y(x)= |a|*e^(bx+cx^2)

Option Explicit
    Dim h As Single
    Dim b As Single
    Dim a As Single
    Dim c As Single
    Dim x As Single
    Dim Xn As Single
    Dim Xk As Single
 
Private Function f(x As Single) As Single
f = Abs(a) * Exp(b * x + c * x ^ 2)
End Function
Private Sub Command1_Click()
a = Val(txt_a)
b = Val(txt_b)
c = Val(txt_c)
Xn = Val(txt_xn)
Xk = Val(txt_xk)
    For x = Xn To Xk Step h
f = Abs(a) * Exp(b * x + c * x ^ 2)
    Next x
txt_f = f
End Sub

f = Abs(a) * Exp(b * x + c * x ^ 2)

r = f(x)

For x = Xn To Xk Step h
        R = f(x)
    Next x
Txt_f = R

Private Sub Command1_Click()
'Х нач. до Х кон. с шагом Н  : y(x)= |a|*e^(bx+cx^2)
 
Dim x11, x21, h1
Dim x1#, x2#, h#, F#, minF#, maxF#
Dim x#, k%
a = -3: b = 5: c = 7
x11 = Replace(InputBox("X нач.- ,", , 0), ".", ",")
x21 = Replace(InputBox("X кон.- ,", , 2), ".", ",")
h1 = Replace(InputBox("шаг H- ,", , 0.1), ".", ",")
If IsNumeric(x11) And IsNumeric(x21) And IsNumeric(h1) Then
x1 = CSng(x11): x2 = CSng(x21): h = CSng(h1)
k = 0
minF = Abs(a) * Exp(b * x + c * x ^ 2): maxF = minF
For x = x1 + h To x2 Step h
k = k + 1
If k > 10000 Then
MsgBox "очень мелкий шаг"
Exit Sub
End If
On Error GoTo err
F = Abs(a) * Exp(b * x + c * x ^ 2)
If minF > F Then minF = F
If maxF < F Then maxF = F
Next x
Print "minF = "; minF
Print "maxF = "; maxF
Else
MsgBox "Некорректный ввод!"
End If
Exit Sub
err: MsgBox "Переполнение!"
End Sub