Im just learned basic code can u show me where I is wrong?

#include<iostream>
#include<math.h>
using namespace std;
void main()
{
	int a, b, c, d;
	double  x, x0, x1, x2;
	cout << "nhap a,b,c";
	cin >> a >> b >> c;
	if (a == 0)
	{
		if (b == 0)
			cout << " a va b khong dong thoi bang khong moi ban nhap lai" << endl;
		else
			x0 = -c / b;
		cout << x0 << endl;
	else
	{


		d = b*b - 4 * a*c;
		if (d < 0)
		{
			cout << "phuong trinh vo nghiem" << endl;
		}
		if (d == 0)
		{
			x = -b / (2 * a);
			cout << "nghiem kep cua phuong tring" << x << endl;
		}
		if (d > 0)
		{

			x1 = (-b + sqrt(d)) / (2 * a);
			x2 = (-b - sqrt(d)) / (2 * a);
			cout << "nghiem 1 cua phuong tring la" << x1 << endl;
			cout << "nghiem 2 cua phuong tring la" << x2 << endl;
		}
	}


	system("pause");

	}
}