Add source code of Lesson 2

Bai thuc hanh so 2/bai1.cpp

@@ -0,0 +1,18 @@
+#include <iostream>
+
+using namespace std;
+
+int main(){
+  int n;
+  cout << "Nhap so tien khach hang phai tra: ";
+  cin >> n;
+  float ans=n;
+  if (n>=200 && n<300){
+    ans-=n*0.2;
+  }
+  else if (n>=300){
+    ans-=n*0.3;
+  }
+  cout << "So tien khach hang phai tra la: " << ans << "\n";
+  return 0;
+}

Bai thuc hanh so 2/bai2.cpp

@@ -0,0 +1,33 @@
+#include <iostream>
+#include <math.h>
+
+using namespace std;
+
+int main(){
+  float a,b,c;
+  cout << "Nhap a: ";
+  cin >> a;
+  cout << "Nhap b: ";
+  cin >> b;
+  cout << "Nhao c: ";
+  cin >> c;
+  if (a==0){
+    cout << "Phuong trinh tren khong phai phuong trinh bac 2.\n";
+  }
+  else{
+    float delta = b*b-4*a*c;
+    if (delta<0){
+      cout << "Phuong trinh vo nghiem.\n";
+    }
+    else if (delta == 0){
+      float ans = -b/(2*a);
+      cout << "Phuong trinh tren co nghiem kep la " << ans << ".\n";
+    }
+    else{
+      float n1 = (-b+sqrt(delta))/(2*a);
+      float n2 = (-b-sqrt(delta))/(2*a);
+      cout << "Phuong trinh tren co 2 nghiem phan biet la " << n1 << " va " << n2 << ".\n";
+    }
+  }
+  return 0;
+}

Bai thuc hanh so 2/bai3.cpp

@@ -0,0 +1,22 @@
+#include <iostream>
+#include <math.h>
+
+using namespace std;
+
+int main(){
+  float x;
+  int n;
+  cout << "Nhap vao mot so thuc x: ";
+  cin >> x;
+  cout << "Nhap vao mot so nguyen n: ";
+  cin >> n;
+  float s=0;
+  if (n%2==0){
+    s+=2016*x;
+    for (int i=2;i<=n;i++){
+      s+=(pow(x,i)/pow(3,i-1));
+    }
+  }
+  cout << "S = " << s << "\n";
+  return 0;
+}

Bai thuc hanh so 2/bai4.cpp

@@ -0,0 +1,28 @@
+#include <iostream>
+#include <math.h>
+
+using namespace std;
+
+bool nguyento(int n){
+  if (n<2) return false;
+  for (int i=2;i<=sqrt(n);i++){
+    if (n%i==0) return false;
+  }
+  return true;
+}
+
+int main(){
+  int n;
+  cout << "Nhap n: ";
+  cin >> n;
+  int sum=0,count=0;
+  for (int i=1;i<=n;i++){
+    if (nguyento(i)==true){
+      sum+=i;
+      count++;
+    }
+  }
+  cout << "Co " << count << " so nguyen to trong doan tu 1 den " << n << ".\n";
+  cout << "Tong cua chung la " << sum << ".\n";
+  return 0;
+}

Bai thuc hanh so 2/bai5.cpp

@@ -0,0 +1,24 @@
+#include <iostream>
+
+using namespace std;
+
+int main(){
+  int n;
+  cout << "Nhap so kWh dien tieu thu trong thang: ";
+  cin >> n;
+  long long ans;
+  if (n<=100){
+    ans=n*750;
+  }
+  else if (n>100 && n<=200){
+    ans=100*750+(n-100)*1250;
+  }
+  else if (n>200 && n<=300){
+    ans=100*750+100*1250+(n-200)*1750;
+  }
+  else{
+    ans=100*750+100*1250+100*1750+(n-300)*3000;
+  }
+  cout << "So tien dien ho tren phai tra la " << ans << " VND.\n";
+  return 0;
+}