Возникновение странных погрешностей около нуля и возникающие из-за нее косяки

#include <iostream>
#include <fstream>
#include <cstdlib>
#include <stdlib.h>
#include <conio.h>
#include <time.h>
#define _USE_MATH_DEFINES
#include <math.h>
using namespace std;
 
double func_de_jong (double, double);
 
int main(){
    setlocale(0,"");
    ofstream(out);
    out.open("01.txt");
    cout << "Start";
    for (int i = 0; i < 1000; i++){
        cout << ".";
        for (int j = 0; j < 1000; j++){
            double point1 = -5 + (double)i * .01;
            double point2 = -5 + (double)j * .01;
            out << "" << point1 << " " << point2 << " " << func_de_jong(point1,point2) << endl;
        }
    }
    out.close();
    cout << "Done!" << endl;
    double x = -1, y = 1.05;
    double a = 100 * (pow(x,2) - y);
    cout << "a = "<< a << endl;
    double b = pow((1 - x), 2);
    cout << "b = "<< b << endl;
    double c = a + b +1;
    cout << "c = "<< c << endl;
    double d = -100/c;
    cout << "d = "<< d << endl;
    double f = d + 100;
    cout << "f = "<< f << endl;
    getch();
    return 0;
}
double func_de_jong (double x, double y){
    double result = 0;
    result = (-100 / (100 * (pow((double)x,2) - y) + pow((double)(1 - x),2) + 1)) + 100;
    return result;
}