c++程序设计——实验3

1．   已知一函数 



 ，输入x的值，求解并输出相应的y值。

#include <iostream>
using namespace std;

int main()
{
float x = 0.0,y = 0.0;
cout << "x=";
cin >> x;
if( x<1 )
{
cout << "y=" << x << endl;
}
else if( (x >= 1)&&(x < 10) )
{
cout << "y=" << 2*x-1 << endl;
}
else
{
cout << "y=" << 3*x-11 << endl;
}
return 0;
}
2．   求一元二次方程ax2+bx+c=0的根，其中a、b、c为实数，由键盘输入。

#include <iostream>
#include <math.h>
using namespace std;

int main()
{
double a=0.0,b=0.0,c=0.0;
cout << "请输入二元一次方程的系数：" << endl;
cin >> a >> b >> c;
double delta = b*b-4*a*c;
if( delta < 0 )
{
cout << "方程无实解！" << endl;
}
else if( delta == 0)
{
double x = -b/(2*a);
cout << "方程只有一个解：" << endl;
cout << x << endl;
}
else
{
double q = sqrt(delta);
double x1 = (-b-q)/(2*a);
double x2 = (-b+q)/(2*a);
cout << "方程的两个不同的解：" <<endl;
cout << x1 << endl;
cout << x2 << endl;
}
return 0;
}