VBA Code

Custom Worksheet Function - Quadratic Equation

Public Function QUADRATIC(sngValueA As Single, _ 
                          sngValueB As Single, _ 
                          sngValueC As Single) As Variant 

Dim vReturnArray() As String 
Dim sngDeterminant As Single 
Dim sngreal As Single 
Dim sngimaginary As Single 
  
   Call Application.Volatile(True) 
   ReDim vReturnArray(2) 
   
   If sngValueA = 0 Then Call MsgBox("The value of A cannot be 0") 
   If sngValueA = 0 Then Exit Function 

   sngDeterminant = (sngValueB * sngValueB) - (4 * sngValueA * sngValueC) 
   
   Select Case sngDeterminant 
   
      Case Is < 0 
         vReturnArray(0) = "Two Complex" 
   
         sngreal = -sngValueB / (2 * sngValueA) 
         sngimaginary = VBA.Sqr(-sngDeterminant) / (2 * sngValueA) 
                  
         If sngreal <> 0 Then vReturnArray(1) = VBA.Round(sngreal, 2) 
         If sngreal <> 0 Then vReturnArray(2) = VBA.Round(sngreal, 2) 
         
         If sngreal <> 0 And sngimaginary <> 0 Then 
            vReturnArray(1) = vReturnArray(1) & "+" 
            vReturnArray(2) = vReturnArray(2) & "-" 
         End If 
         If sngimaginary <> 0 Then 
            vReturnArray(1) = vReturnArray(1) & VBA.Round(sngimaginary, 2) & "i" 
            vReturnArray(2) = vReturnArray(2) & -VBA.Round(sngimaginary, 2) & "i" 
         End If 
            
      Case Is = 0 
         vReturnArray(0) = "One Real" 
         vReturnArray(1) = -sngValueB / (2 * sngValueA) 
         vReturnArray(1) = VBA.Round(vReturnArray(1), 3) 
         
         vReturnArray(2) = "-" 
   
      Case Is > 0 
         vReturnArray(0) = "Two Real" 
         vReturnArray(1) = (-sngValueB + VBA.Sqr(sngDeterminant)) / (2 * sngValueA) 
         vReturnArray(1) = VBA.Round(vReturnArray(1), 3) 
         
         vReturnArray(2) = (-sngValueB - VBA.Sqr(sngDeterminant)) / (2 * sngValueA) 
         vReturnArray(2) = VBA.Round(vReturnArray(2), 3) 
         
   End Select 

   QUADRATIC = vReturnArray 
End Function