#include <stdio.h>
#include <math.h> 

#define N 4

int main(void)
{
	double A[N][N]={{2,1,4,1},{3,4,-1,-1},{1,-4,1,5},{2,-2,1,3}}, b[N]={-4,3,9,7}, x[N]={0};
	int i,j,k;

	printf("Antes do escalonamento: \n");
	for (i=0;i<N;i++)
	{
		for (j=0;j<N;j++)
		{
			printf("%8.3lf",A[i][j]);

			if (j==(N-1))
				printf("\n");
			else 
				printf(" ");
		}
	}

	for (i=0;i<N;i++)
	{
		for (j=i+1;j<N;j++)
		{
			double c=A[j][i]/A[i][i];

			for (k=i;k<N;k++)
			{
				A[j][k]=A[j][k] - c*A[i][k];
			}

			b[j]=b[j]-c*b[i];
		}
	}

	printf("Após o escalonamento: \n");
	for (i=0;i<N;i++)
	{
		for (j=0;j<N;j++)
		{
			printf("%8.3lf",A[i][j]);

			if (j==(N-1))
				printf("\n");
			else 
				printf(" ");
		}
	}


	for (i=N-1;i>=0;i--)
	{
		double soma = b[i];

		for (j=i+1;j<N;j++)
		{
			soma=soma-A[i][j]*x[j];
		}

		x[i]=soma/A[i][i];
	}

	printf("Solução: \n");
	for (i=0;i<N;i++)
	{
		printf("%8.3lf",x[i]);

		if (i==(N-1))
			printf("\n");
		else 
			printf(" ");	
	}


	return 0;
}