Untitled

Bai 3:

#include <iostream>

using namespace std;

int main() {
    int so;
    cout << "Nhap so: ";
    cin >> so;

    if (so >= 0 && so <= 9) {
        cout << "So ban nhap lai: " << so << endl;
    } else {
        cout << "Khong doc duoc." << endl;
    }

    return 0;
}


Bai 4 : 


#include <iostream>
#include <cctype> 

using namespace std;

int main() {
    char a;
    
    cout << "Nhap chu: ";
    cin >> a;

    if (islower(a)) { 
        a = toupper(a); 
    } else if (isupper(a)) { 
        a = tolower(a); 
    }

    cout << "Sau khi doi : " << a << endl;

    return 0;
}


Bai 5 : 


#include <iostream>

using namespace std;

int main() {
    float a, b;

    cout << "Nhap a: ";
    cin >> a;

    cout << "Nhap b: ";
    cin >> b;

    if (a == 0) {
        if (b == 0) {
            cout << "PT vo so nghiem." << endl;
        } else {
            cout << "PT vo nghiem." << endl;
        }
    } else {
        float x = -b / a;
        cout << "Nghiem PT la x = " << x << endl;
    }

    return 0;
}

Bai 6: 

#include <iostream 
#include <cmath>

using namespace std;

int main() {
    float a, b, c;
    cout << "Nhap a: ";
    cin >> a;
    cout << "Nhap b: ";
    cin >> b;
    cout << "Nhap c: ";
    cin >> c;

    
    float delta = b * b - 4 * a * c;

    if (delta > 0) {
        
        float x1 = (-b + sqrt(delta)) / (2 * a);
        float x2 = (-b - sqrt(delta)) / (2 * a);
        cout << "Nghiem x1 = " << x1 << endl;
        cout << "Nghiem x2 = " << x2 << endl;
    } else if (delta == 0) {
        
        float x = -b / (2 * a);
        cout << "Nghiem kep x = " << x << endl;
    } else {
        
        cout << "PT khong coa nghiem" << endl;
    }

    return 0;
}

Bai 7 :

#include <iostream>

using namespace std;

int main() {
    int a, b, c, d;

    cout << "Nhap a: ";
    cin >> a;
    
    cout << "Nhap b: ";
    cin >> b;
    
    cout << "Nhap c: ";
    cin >> c;
    
    cout << "Nhap d: ";
    cin >> d;

    int max = a; // đây là giả sử nghen

    
    if (b > max) {
        max = b;
    }

    
    if (c > max) {
        max = c;
    }

   
    if (d > max) {
        max = d;
    }

    cout << "So lon nhat la : " << max << endl;

    return 0;
}


Bai 9 : 


#include <iostream>
#include <iomanip> 

using namespace std;

int main() {
    float quangduong;
    float tongxeng = 0;

    cout << "Nhap quang duong di taxi (km): ";
    cin >> quangduong;

    

   if (quangduong <= 1) {
        tongxeng = 1500;
    } else if (quangduong <= 5) {
        tongxeng = 1500 + (quangduong - 1) * 13500;
    } else {
        tongxeng = 1500 + 4 * 13500 + (quangduong - 5) * 11000;
    }

    if (quangduong > 120) {
        // giam 10%
        float giamgia = tongxeng * 0.1;
        tongxeng -= giamgia;
    }

    cout << fixed << setprecision(2);
    cout << "Tong: " << tongxeng << " dong " << endl;

    return 0;
}



Bai 8 :

#include <iostream>

using namespace std;

int main() {
    int a, b, c, d;

    cout << "Nhap a: ";
    cin >> a;

    cout << "Nhap b: ";
    cin >> b;

    cout << "Nhap c: ";
    cin >> c;

    cout << "Nhap d: ";
    cin >> d;

    
    int hoandoi;
    if (a > b) {
        hoandoi = a;
        a = b;
        b = hoandoi;
    }
    if (b > c) {
        hoandoi = b;
        b = c;
        c = hoandoi;
    }
    if (c > d) {
        hoandoi = c;
        c = d;
        d = hoandoi;
    }
    if (a > b) {
        hoandoi = a;
        a = b;
        b = hoandoi;
    }
    if (b > c) {
        hoandoi = b;
        b = c;
        c = hoandoi;
    }
    if (a > b) {
        hoandoi = a;
        a = b;
        b = hoandoi;
    }

    cout << "Ket qua: " << a << " " << b << " " << c << " " << d << endl;

    return 0;
}