3.1 #include <iostream>
using namespace std;

int main()
{int a,b,c;
cout<<"a"<<endl;
cin>>a;
cout<<"b"<<endl;
cin>>b;
cout<<"c"<<endl;
cin>>c;
float d;
d=b*b-(4*a*c);
if (d>0)
cout<<"имеет 2 решения"<<endl;
if (d=0)
cout << "имеет 1 решение"<<endl;
else
cout <<"не имеет решение"<<endl;

return 0;
}

3.2 #include <iostream>
using namespace std;
int main()
{
    int a, b;

    cout << "Ведите числа"<< endl;
    cin >> a;
    cin >> b;
 if (a > b)
        cout <<"Max is "<< a <<endl;
 if (a==b)
        cout <<"Числа равны"<< endl;
    else
        cout << "Max is "<< b << endl;
 return (0);
}
3.3 #include <iostream>
using namespace std;
int main()
{
  int a,b,c,d;
cout<<"a"<<endl;
cin>>a;
cout<<"b"<<endl;
cin>>b;
cout<<"c"<<endl;
cin>>c;
cout<<"d"<<endl;
cin>>d;
if (a<b&&a<c&&a<d)
cout<<"min is "<< a <<endl;
if (a>b&&b<c&&b<d)
cout<< "min is "<< b <<endl;
if (c<a&&c<b&&c<d)
cout<<"min is "<< c <<endl;
if(d<a&&d<b&&d<c)
cout<<"min is "<< d <<endl;
return (0);
}
3.4
#include <iostream>
using namespace std;
int main()
{
setlocale(0, "");
int i, j;
int summa=0 ;
cout << "Введите первое число: "<<endl;
cin >> i;
cout << "Введите второе число: "<<endl;
cin >> j;
for (i; i<=j; i++) {
summa = summa + i*i;
}
cout << summa <<endl;
return 0;
}