поразряд

#define _CRT_SECURE_NO_WARNINGS
#include<iostream>
#include<string>
#include<alg.h>

using namespace std;
const double EPS = 1e-4;
const int INF = 1e8 + 13;



double func(double x)
{
    return 2. * x*x - 6 * x - 3;
}

pair<double, double> solve()
{

    double left = -1;
    double right = 3;
    double step = 0.1;
    double answer = INF;
    double answerPoint = -INF;
    while (step >= EPS)
    {
        step /= 2;
        for (double i = left; i <= right; i += step)
        {
            double cur = func(i);
            if (answer == INF)
            {
                answer = cur;
                continue;
            }
            if (cur <= answer)
            {
                answer = cur;
                answerPoint = i;
            }
            else
            {
                right = min(i + step, right);
                break;
            }
        }
        step /= 2;
        for (double i = right; i >= left; i -= step)
        {
            double cur = func(i);
            if (cur <= answer)
            {
                answer = cur;
                answerPoint = i;
            }
            else
            {
                left = max(i - step, left);
                break;
            }
        }
    }
    return make_pair(answer, answerPoint);
}

int main()
{
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);

    pair<double, double> ans = solve();
    cout << "min = " << ans.first << "\nwith x =  " << ans.second << endl;

}