#include <iostream>
#include <conio.h>
#include <math.h>

using namespace std;

void BaiToan1() {
	int a,b;
	cout<<"Nhap 2 so nguyen a,b: "; cin>>a>>b;
	cout<<"Tong a + b la: "<<a+b<<endl;
	cout<<"Hieu a - b la: "<<a-b<<endl;
	cout<<"Tich a * b la: "<<a*b<<endl;
	if (b != 0) {
		cout<<"Thuong a / b la: "<<(float)a/b<<endl;
		cout<<"Phan nguyen: "<<a/b<<endl;
		cout<<"Phan du: "<<a%b<<endl;
	} else {
		cout<<"b phai khac 0";
	}
}

void BaiToan2() {
	float fx, x;
	cout<<"Nhap vao gia tri x: "; cin>>x;
	fx = (pow(x,2) + exp(x) + pow(sin(x),2)) / sqrt(pow(x,2) + 1);
	cout<<"F(x) = "<<fx;
}

void BaiToan3() {
	float tien,tong,km;
	cout<<"Nhap so tien phai tra: "; cin>>tien;
	if (tien >= 200000 && tien <= 300000) {
		km = 20;
	} else if (tien > 300000) {
		km = 30;
	} else {
		km = 0;
	}
	tong = tien - tien*km/100;
	cout<<"So tien phai tra: "<<tien<<endl;
	cout<<"Khuyen mai: "<<km<<"%"<<endl;
	cout<<"So tien phai ra sau KM: "<<tong;
}

void BaiToan4() {
	float diem;
	cout<<"Nhap vao diem tong ket: "; cin>>diem;
	if (diem < 0 || diem > 10) {
		cout<<"Diem khong hop le";
	} else if (diem >= 8.0 && diem <= 10) {
		cout<<"Xep loai Gioi";
	} else if (diem >= 7.0 && diem < 8.0) {
		cout<<"Xep loai Kha";
	} else if (diem >= 5.0 && diem < 7.0) {
		cout<<"Xep loai Trung Binh";
	} else if (diem >= 3.0 && diem < 5.0) {
		cout<<"Xep loai Yeu";
	} else {
		cout<<"Xep loai Kem";
	}
}

void BaiToan5() {
	float a,b;
	cout<<"Nhap gia tri a,b: "; cin>>a>>b;
	if (a != 0) {
		cout<<"Phuong trinh co 1 nghiem la x = "<<-b/a;
	} else {
		if (b == 0) {
			cout<<"Phuong trinh co vo so nghiem";
		} else {
			cout<<"Phuong trinh vo nghiem";
		}
	}
}

void BaiToan6() {
	int thang;
	cout<<"Nhap vao thang: "; cin>>thang;
	switch (thang) {
		case 1:
		case 3:
		case 5:
		case 7:
		case 8:
		case 10:
		case 12: cout<<"Thang co 31 ngay"; break;
		case 4:
		case 6:
		case 9: cout<<"Thang co 30 ngay"; break;
		case 11:
		case 2: cout<<"Thang co 28 ngay"; break;
		default: cout<<"Thang nhap vao khong hop le";
	}
}

main() {
	int luachon;
	cout<<"\tMENU LUA CHON"<<endl;
	cout<<"- Bam phim 1 de lua chon giai bai toan 1"<<endl;
	cout<<"- Bam phim 2 de lua chon giai bai toan 2"<<endl;
	cout<<"- Bam phim 3 de lua chon giai bai toan 3"<<endl;
	cout<<"- Bam phim 4 de lua chon giai bai toan 4"<<endl;
	cout<<"- Bam phim 5 de lua chon giai bai toan 5"<<endl;
	cout<<"- Bam phim 6 de lua chon giai bai toan 6"<<endl;
	cout<<"- Bam phim 0 de lua chon dong ung dung"<<endl;
	cout<<"Nhap lua chon cua ban: "; cin>>luachon;
	switch (luachon) {
		case 1: BaiToan1(); break;
		case 2: BaiToan2(); break;
		case 3: BaiToan3(); break;
		case 4: BaiToan4(); break;
		case 5: BaiToan5(); break;
		case 6: BaiToan6(); break;
		case 0: exit(0);
		default: cout<<"Lua chon khong dung";
	}
}