public static void Main()
double[,] a= new double[2,3];
Console.WriteLine("Introdueix el "+(i+1)+" vector");
a[i,0]= double.Parse(Console.ReadLine());
a[i,1]= double.Parse(Console.ReadLine());
a[i,2]= double.Parse(Console.ReadLine());
if(a[1,0]/a[0,0]==a[1,1]/a[0,1]&&a[1,1]/a[0,1]==a[1,2]/a[0,2]){
Console.WriteLine("Els dos vectors ["+a[0,0]+","+a[0,1]+","+a[0,2]+"] i ["+a[1,0]+","+a[1,1]+","+a[1,2]+"] són proporcionals.") ;
Console.WriteLine("Els vectors no són proporcionals.");