Add source code of Lesson 3B

Bai thuc hanh so 3B/bai1.cpp

@@ -0,0 +1,23 @@
+#include <iostream>
+
+using namespace std;
+
+long giaithua(int n){
+  if (n==1){
+    return 1;
+  }
+  else{
+    return (n*giaithua(n-1));
+  }
+}
+
+int main(){
+  int a,b;
+  cout << "Nhap so nguyen a: ";
+  cin >> a;
+  cout << "Nhap so nguyen b: ";
+  cin >> b;
+  float ans=(float)(giaithua(a)+giaithua(b))/giaithua(a+b);
+  cout << "(a!+b!)/(a+b)! = " << ans << "\n";
+  return 0;
+}

Bai thuc hanh so 3B/bai2.cpp

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+#include <iostream>
+
+using namespace std;
+
+float f(float x, int n){
+  if (n==1) return x;
+  else return (x/n*f(x,n-1));
+}
+
+int main(){
+  float x;
+  cout << "Nhap so thuc x: ";
+  cin >> x;
+  int n;
+  cout << "Nhap so nguyen n: ";
+  cin >> n;
+  float ans=f(x,n);
+  cout << "f(x,n) = " << ans << "\n";
+  return 0;
+}

Bai thuc hanh so 3B/bai3.cpp

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+#include <iostream>
+#include <math.h>
+
+using namespace std;
+
+float f(float x, int n){
+  if (n==0) return 2017;
+  else return (pow(x,n)+f(x,n-1));
+}
+
+int main(){
+  float x;
+  cout << "Nhap so thuc x: ";
+  cin >> x;
+  int n;
+  cout << "Nhap so nguyen n: ";
+  cin >> n;
+  float ans=f(x,n);
+  cout << "f(x,n) = " << ans << "\n";
+  return 0;
+}

Bai thuc hanh so 3B/bai4.cpp

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+#include <iostream>
+
+using namespace std;
+
+int dem(int n){
+  if (n>=0 && n<=9) return 1;
+  else return (dem(n/10)+1);
+}
+
+int main(){
+  int n;
+  cout << "Nhap so nguyen n: ";
+  cin >> n;
+  cout << "So nguyen " << n << " co " << dem(n) << " chu so.\n";
+  return 0;
+}

Bai thuc hanh so 3B/bai5.cpp

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+#include <iostream>
+
+using namespace std;
+
+int catalan(int n){
+  if (n==1 || n==2) return 1;
+  else{
+    int t=0;
+    for (int i=0;i<n;i++){
+      t+=catalan(i)*catalan(n-i);
+    }
+    return t;
+  }
+}
+
+int main(){
+  int n;
+  cout << "Nhap so nguyen duong n: ";
+  cin >> n;
+  cout << "Chu so CataLan thu " << n << " la " << catalan(n) << "\n";
+  return 0;
+}