Okay, i finished first step, i wonder if it's good :P anyways it's working ... about the area i personally think that it would be the best to find 2 points with the biggest distance and make them be the part of the ellipse and other points would be inside.. but i don't know if i'm not wrong. That's what i have for now.

Code:

#include <stdio.h>
#include <math.h>
#include <stdlib.h>
#include <time.h>
void main()
{
srand( (unsigned) time(NULL));
int x,y;
double x_min = -100;
double x_max = 100;
double y_min = -100;
double y_max = 100;
int i,n;
int lp=0;
printf("Input the number of points:\n");
scanf(" %ld",&n);
for(i = 0; i<n; i++)
{
x = rand() * (x_max - x_min) / (double) RAND_MAX + x_min;
y = rand() * (y_max - y_min) / (double) RAND_MAX + y_min;
printf("\n(%ld;%ld)",x,y);
}
return x,y;
}