Was ist Falsch?

#include "BinomischeGleichung3.h"
#include <math.h>
//---------------------------------------------------------------------------
#pragma resource "*.dfm"
TForm1 *Form1;
int a,b,c, p, q, x, x13, x15, x14, x12, x16, x1, x2;
//---------------------------------------------------------------------------
__fastcall TForm1::TForm1(TComponent* Owner)
	: TForm(Owner)
{
}
//---------------------------------------------------------------------------
void __fastcall TForm1::Button1Click(TObject *Sender)
{
float a = StrToInt (Edit1->Text);
float b = StrToInt (Edit2->Text);
float c = StrToInt (Edit3->Text);
float x  =  1;
float p =  b/ a;
float q  = c / a;

 x13 = - p / 2;
 x15 = x13 * x13;
 x14 = x12 - q;
 x12 = sqrt(x14);
float x16 = sqrt (x12);
x1 = x16;
x2 = -x16;
//(x + p/2)² = (p/2)² -q

 Label5->Caption = "Ergf" +IntToStr (x1);
Label4->Caption = "Ergebnis bis jetzt" +IntToStr (x2);
}

wie soll das funktionieren, wenn x12 noch nicht initialisiert wurde?