c++第四次作业

#include <iostream>
using namespace std;
int main()
{
int a=1,b=1;
double sum=0;
while(a<=19)
{
sum=sum+b*1.0*a/(a+2);
a=a+2;
b=-b;
}
cout<<"结果为"<<sum<<endl;
return 0;
}

#include <iostream>
using namespace std;
int main()
{
int x,y,z;
for(x=0;x<=20;x++)
for(y=0;y<=33;y++)
for(z=0;z<=300;z=z+3)
if(5*x+3*y+z/3==100&&x+y+z==100)
{
cout<<"鸡翁"<<x<<"鸡母"<<y<<"鸡雏"<<z<<endl;
}
return 0;
}

#include <iostream>
using namespace std;
int main( )
{
int a,b,n=6;
for(a=1,b=1; b<=5;b++)
cout<<" ";
cout<<"*"<<endl;
for(a=2;a<=5;a++)
{
for(b=1;b<=6-a;b++)
cout<<" ";
cout<<"*";
for(b=1; b<=2*a-3;b++)
cout<<" ";
cout<<"*"<<endl;
}
if(a==6)
cout<<"***********";
cout<<endl;
return 0;
}