Получившийся код

Option Explicit

Private Sub Text3_Change()

End Sub

Private Sub cmdCalculate_Click()

Dim paramA As Double

Dim paramB As Double

Dim paramC As Double

Dim x1 As Double

Dim x2 As Double

Dim D As Double

paramA = Val(txtParamA.Text)

paramB = Val(txtParamB.Text)

paramC = Val(txtParamC.Text)

If paramA = 0 Or paramB = 0 Or paramC = 0 Then

MsgBox "Нули в качестве коэффициентов не допускаются!", _

vbCritical

Exit Sub

End If

D = CalcDiscremenant(paramA, paramB, paramC)

If D > 0 Then

x1 = (paramB + Sqr(D)) / (2 * paramA)

x2 = (paramB - Sqr(D)) / (2 * paramA)

WriteResultsInLabels "Дискриминант: " & D, _

"Корень №1: " & x1, "Корень №2: " & x2

ElseIf D = 0 Then

x1 = paramB / (2 * paramA)

x2 = x1

WriteResultsInLabels "Дискриминант: " & D, _

"Корень №1: " & x1, "Корень №2 = Корню №1"

ElseIf D < 0 Then

WriteResultsInLabels "Дискриминант: " & D, _

"Корней нет!", ""

MsgBox "Дискриминант меньше нуля! Корней нет!", vbCritical

End If

End Sub

Public Function CalcDiscremenant(ByVal a As Double, _

ByVal b As Double, ByVal c As Double) As Double

CalcDiscremenant = (b * b) - (4 * a * c)

End Function

Public Sub WriteResultsInLabels(lblDCapt As String, _

lblX1Capt As String, lblX2Capt As String)

lblD.Caption = lblDCapt

lblX1.Caption = lblX1Capt

lblX2.Caption = lblX2Capt

End Sub

Private Sub Form_Load()

End Sub

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