C语言程序设计教程（第三版）课后习题8.2 （C++代码）

/*求方程 的根，用三个函数分别求当b^2-4ac大于0、等于0、和小于0时的根，并输出结果。从主函数输入a、b、c的值。*/ 

#include<iostream>

#include<iomanip>

#include<cmath>

using namespace std;

void getEquation(double a, double b, double c);

double delt;

int main()

{

double a, b, c;

cin >> a >> b >> c;

getEquation(a, b, c); 

return 0;

}

void getEquation(double a, double b, double c)

{

double x1, x2;

delt = b * b - 4 * a * c;

if(delt<0)

{

delt=-delt;

cout<<"x1="<<setprecision(3)<<setiosflags(ios::fixed)<<-b/(2*a)<<'+'<<sqrt(delt)/(2*a)<<'i'<<' ';

cout<<"x2="<<setprecision(3)<<setiosflags(ios::fixed)<<-b/(2*a)<<'-'<<sqrt(delt)/(2*a)<<'i'<<endl;

}

else

{

cout<<"x1="<<setprecision(3)<<setiosflags(ios::fixed)<<-(b+sqrt(delt))/(2*a)<<' ';

cout<<"x2="<<setprecision(3)<<setiosflags(ios::fixed)<<-(b-sqrt(delt))/(2*a)<<endl;

}

}