Takie se

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

float a,b,c,x1,x2,i;
int n;

float calcY(x){
    return a*pow(x,2)+b*x+c;
}
int main()
{
    FILE *filestream;
    filestream = fopen("out.txt","w");
    do{
        printf("\nPodaj zakres (x1 < x2) : ");
        scanf("%f %f", &x1,&x2);
    }while(x2<x1 || x2==x1);
    printf("\n===\n");


    do{
        printf("\nPodaj ilosc probek: ");
        scanf("%d",&n);
    }while(n<2);
    printf("\n===\n");

    do{
        printf("\nPodaj wspolczynnik a: "); scanf("%f",&a);
        printf("\nPodaj wspolczynnik b: "); scanf("%f",&b);
        printf("\nPodaj wspolczynnik c: "); scanf("%f",&c);
    }while(a==0 || b==0 || c==0);

    float step = abs((x2-x1))/n*1.00;

    for(i=1;i<=n;i++)
         fprintf(filestream, "X:%f \t Y:%f \n",x1+step*n, calcY(x1+step*n));

    fclose(filestream);
    return 0;
}