Answer to Question #291979 in Visual Basic for Lam

Question

Write a visual basic code that will compute root of a quadratic equation using determinant

Answer 1

Module Module1
    ''' <summary>
    ''' A function named getDiscriminant() that returns the discriminant, which is b2 - 4ac.
    ''' </summary>
    ''' <param name="a"></param>
    ''' <param name="b"></param>
    ''' <param name="c"></param>
    ''' <returns></returns>
    ''' <remarks></remarks>
    Function getDiscriminant(ByVal a As Double, ByVal b As Double, ByVal c As Double) As Double
        Return b * b - 4 * a * c
    End Function


    ''' <summary>
    ''' The functions named getRoot1() and getRoot2() for returning two roots of the equation:
    ''' These functions are useful only if the discriminant is non-negative. 
    ''' Let these functions return 0 if the discriminant is negative.
    ''' </summary>
    ''' <param name="a"></param>
    ''' <param name="b"></param>
    ''' <param name="c"></param>
    ''' <param name="root"></param>
    ''' <returns></returns>
    ''' <remarks></remarks>
    Function getRoot1(ByVal a As Double, ByVal b As Double, ByVal c As Double, ByVal root As Integer) As Double
        Dim D As Double = getDiscriminant(a, b, c)
        If (D < 0) Then
            Return 0
        End If
        If root = 1 Then
            Return ((-1) * b + Math.Sqrt(D)) / (2 * a)
        End If
        Return ((-1) * b - Math.Sqrt(D)) / (2 * a)
    End Function


    Sub Main()
        Console.Write("Enter a: ")
        Dim a As Double = Double.Parse(Console.ReadLine())
        Console.Write("Enter b: ")
        Dim b As Double = Double.Parse(Console.ReadLine())
        Console.Write("Enter c: ")
        Dim c As Double = Double.Parse(Console.ReadLine())
        Dim D As Double = getDiscriminant(a, b, c)
        'If the discriminant is positive, display the two roots. 
        If (D > 0) Then
            Console.WriteLine("Root 1 = " + getRoot1(a, b, c, 1).ToString())
            Console.WriteLine("Root 2 = " + getRoot1(a, b, c, 2).ToString())
        ElseIf (D = 0) Then
            'If the discriminant is 0, display the one root. 
            Console.WriteLine("Root 1 = " + getRoot1(a, b, c, 1).ToString())
        Else
            'Otherwise, display "The equation has no real roots".
            Console.WriteLine("The equation has no real roots")
        End If


        Console.ReadLine()
    End Sub




End Module