Ecuatia de gradul 2

//ecuatia de gradul 2
#include<conio.h>
#include<iostream.h>
#include<math.h>
int main()
{float a,b,c,d,X1,X2;
cout<<"aX^2+bX+c=0"<<endl;
cout<<"Introduceti valori lui a,b si c: "<<endl;
cout<<"a= ";cin>>a;
cout<<"b= ";cin>>b;
cout<<"c= ";cin>>c;
d=pow(b,2)-4*a*c;
if(d>=0)
{X1=(-b+sqrt(d))/2*a;
X2=(-b-sqrt(d))/2*a;
cout<<"X1= "<<X1<<endl<<"X2= "<<X2;
}
else
{cout<<"X1="<<-b/2*a<<"+i"<<sqrt(d)/2*a<<endl;
cout<<"X2="<<-b/2*a<<"-i"<<sqrt(d)/2*a<<endl;
cout<<"X1 , X2 APARTINE LUI C(numere complexe)";
}
getche();
}

Sir caractere - transformare litere

//litere mari-> mici
#include<iostream.h>
#include<conio.h>
#include<string.h>
int main()
{char sir[100];
cout<<"Introduceti sirul: "<<endl;
cin.get(sir,100);
strlwr(sir);
cout<<sir;
getche();}


//litere mici->mari
#include<iostream.h>
#include<conio.h>
#include<string.h>
int main()
{char sir[100];
cout<<"Introduceti sirul: "<<endl;
cin.get(sir,100);
strupr(sir);
cout<<sir;
getche();}

maximul si minimul ce se pot forma din cifrele unui numar

//minimul si maximul ce se pot forma din cifrele unui numar
//OBS:numarul nu trebuie sa contina cifra 0
#include<iostream.h>
#include<conio.h>
int main()
{long  n,aux;
int x[100],nr=0,i=1,terminat=0,c;

cout<<"n= ";cin>>n;
while(n!=0)
{x[i]=n%10;
n=n/10;
i++;
nr++;
}
while(!terminat)
{terminat=1;
for(i=1;i<nr;i++)
{if(x[i]>x[i+1])
{aux=x[i];x[i]=x[i+1];x[i+1]=aux;terminat=0;}}
}
n=0;
for(i=1;i<=nr;i++)
n=n*10+x[i];
cout<<"Numarul minim care se poate forma din cifrele lui n este: "<<n<<endl;
aux=0;
while(n!=0)
{c=n%10;
aux=aux*10+c;
n=n/10;}
cout<<"Numarul maxim care se poate forma din cifrele lui n este: "<<aux;
getche();}