Add source code of Lesson 3

Bai thuc hanh so 3/bai1.cpp

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+#include <iostream>
+
+using namespace std;
+
+long giaithua(int n){
+  if (n==1){
+    return 1;
+  }
+  else{
+    return (n*giaithua(n-1));
+  }
+}
+
+int main(){
+  int n;
+  cout << "Nhap so nguyen n: ";
+  cin >> n;
+  double s=(giaithua(n)+1)/giaithua(n+1);
+  cout << "S = " << s << "\n";
+  return 0;
+}

Bai thuc hanh so 3/bai2.cpp

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+#include <iostream>
+
+using namespace std;
+
+float f(float x, int n){
+  return 2*x*x+n*x+n;
+}
+
+int main(){
+  float x,y;
+  cout << "Nhap vao so thuc x: ";
+  cin >> x;
+  cout << "Nhap vao so thuc y: ";
+  cin >> y;
+  int n;
+  cout << "Nhap vao so nguyen n: ";
+  cin >> n;
+  float p=f(x,n)+f(y,n)+f(x+y,n);
+  cout << "P = " << p << "\n";
+  return 0;
+}

Bai thuc hanh so 3/bai3.cpp

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+#include <iostream>
+
+using namespace std;
+
+void nhap(char c,float &n){
+  cout << "Nhap so thuc " << c << ": ";
+  cin >> n;
+}
+
+float max(float a, float b, float c){
+  if (a>=b&&a>=c) return a;
+  if (b>=a&&b>=c) return b;
+  if (c>=a&&c>=b) return c;
+}
+
+float min(float a, float b, float c){
+  if (a<=b&&a<=c) return a;
+  if (b<=a&&b<=c) return b;
+  if (c<=a&&c<=b) return c;
+}
+
+int main(){
+  float a,b,c;
+  nhap('a',a);
+  nhap('b',b);
+  nhap('c',c);
+  float d,e;
+  nhap('d',d);
+  nhap('e',e);
+  cout << "So nho nhat trong 5 so la " << min(min(a,b,c),d,e) << "\n";
+  cout << "So lon nhat trong 5 so la " << max(max(a,b,c),d,e) << "\n";
+  return 0;
+}

Bai thuc hanh so 3/bai4.cpp

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+#include <iostream>
+#include <math.h>
+
+using namespace std;
+
+void nhap(char c,float &n){
+  cout << "Nhap so thuc " << c << ": ";
+  cin >> n;
+}
+
+int ptbh(float a, float b, float c, float &x1, float &x2){
+  float delta=b*b-4*a*c;
+  if (delta<0){
+    return 0;
+  }
+  else if (delta==0){
+    x1=-b/2*a;
+    x2=x1;
+    return 1;
+  }
+  else{
+    x1=(-b+sqrt(delta))/2*a;
+    x2=(-b-sqrt(delta))/2*a;
+    return 2;
+  }
+}
+
+int main(){
+  float a,b,c;
+  nhap('a',a);
+  nhap('b',b);
+  nhap('c',c);
+  float x1,x2;
+  int status = ptbh(a,b,c,x1,x2);
+  if (status==0){
+    cout << "Phuong trinh tren vo nghiem.\n";
+  }
+  else if (status==1){
+    cout << "Phuong trinh tren co nghiem kep x = " << x1 << ".\n";
+  }
+  else{
+    cout << "Phuong trinh tren co 2 nghiem phan biet x1 = " << x1 << " va x2 = " << x2 << ".\n";
+  }
+  return 0;
+}

Bai thuc hanh so 3/bai5.cpp

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+#include <iostream>
+
+using namespace std;
+
+void nhap(char c,float &n){
+  cout << "Nhap so thuc " << c << ": ";
+  cin >> n;
+}
+
+int hept(float a, float b, float c, float d, float e, float f, float &x, float &y){
+  float D=a*e-b*d;
+  float Dx=c*e-b*f;
+  float Dy=a*f-c*d;
+  if (D==0 && Dx==0)
+    return 1;
+  if (D==0 && Dx!=0)
+    return 0;
+  if (D!=0){
+    x=Dx/D;
+    y=Dy/D;
+    return 2;
+  }
+}
+
+int main(){
+  float a,b,c,d,e,f;
+  nhap('a',a);
+  nhap('b',b);
+  nhap('c',c);
+  nhap('d',d);
+  nhap('e',e);
+  nhap('f',f);
+  float x,y;
+  int status = hept(a,b,c,d,e,f,x,y);
+  if (status==0){
+    cout << "He phuong trinh tren vo nghiem.\n";
+  }
+  else if (status==1){
+    cout << "He phuong trinh tren co vo so nghiem.\n";
+  }
+  else{
+    cout << "He phuong trinh tren co mot nghiem x = " << x << " va y = " << y << ".\n";
+  }
+  return 0;
+}