Помогите сделать задачу в с++ 10 вариант

1.
#include <iostream>
#include <locale>

int main() {
    setlocale(LC_ALL, "Russian");
    std::cout << "Введите x:\n";
    double x, fx;
    std::cin >> x;
    if (x >= 8)
        fx = -x * x + x - 9;
    else
        fx = 1 / (x * x * x * x - 6);
    std::cout << "f(x) = " << fx << '\n';
    return 0;
}

2.
#include <iostream>
#include <locale>

int main() {
    setlocale(LC_ALL, "Russian");
    std::cout << "Введите N:\n";
    int n;
    std::cin >> n;
    n = abs(n);
    if (n % 2 == 0 && n > 9 && n < 100)
        std::cout << "Да\n";
    else
        std::cout << "Нет\n";
    return 0;
}

3.
// Код для новичков - без сортировки, без функции min, без swap
#include <iostream>
#include <locale>
#include <cmath>

int main() {
    setlocale(LC_ALL, "Russian");
    std::cout << "Введите x:\n";
    double x;
    std::cin >> x;
    double a = sin(x);
    double b = cos(x);
    if (x > 0) {
        double c = log(x);
        double tmp;
        if (a > c) {
            tmp = a; a = c; c = tmp;
        }
        if (a > b) {
            tmp = a; a = b; b = tmp;
        }
        if (b > c) {
            tmp = b; b = c; c = tmp;
        }
        std::cout << a << ' ' << b << ' ' << c << '\n';
    } else {
        std::cout << "ln(x) не имеет смысла при x <= 0\n";
        if (a <= b)
            std::cout << a << ' ' << b << '\n';
        else
            std::cout << b << ' ' << a << '\n';
    }
    return 0;
}

1)

#include <iostream>
#include <iomanip>
#include <cmath>
using namespace std;
double real(const char* msg) {
cout << msg;
double value;
cin >> value;
cin.ignore(cin.rdbuf()->in_avail());
return value;
}
int main() {
auto x = real("x: ");
double fx;
if (x >= 8) fx = pow(-x, 2) + x - 9;
else fx = 1 / (pow(x, 4) - 6);
cout << "f(" << x << ") = " << fx << endl;
system("pause > nul");
}