编写一个求方程ax^2+bx+c=0的根的程序，用3个函数分别求当b^2-4ac大于零、等于零和小于零时的方程的根。要求从主函数输入a、b、c的值并输出结果-简单

源程序：

#include < iostream>

#include < math.h >

using namespace std;

void equation_1(int a, int b, int c)

{

　　double x1, x2, temp;

　　temp = b*b - 4 * a * c;

　　x1 = (-b + sqrt(temp)) / (2 * a * 1.0);

　　x2 = (-b - sqrt(temp)) / (2 * a * 1.0);

　　cout << "两个不相等的实根" << endl;

　　cout << "x1 = " << x1 << ", x2 = " << x2 << endl;

}

void equation_2(int a, int b, int c)

{

　　double x1, x2, temp;

　　temp = b*b - 4 * a * c;

　　x1 = (-b + sqrt(temp)) / (2 * a * 1.0);

　　x2 = x1;

　　cout << "两个相等的实根" << endl;

　　cout << "x1 = " << x1 << ", x2 = " << x2 << endl;

}

void equation_3(int a, int b, int c)

{

　　double temp, real1, real2, image1, image2;

　　temp = -(b*b - 4 * a * c);

　　real1 = -b / (2 * a *1.0);

　　real2 = real1;

　　image1 = sqrt(temp);

　　image2 = -image1;

　　cout << "两个虚根" << endl;

　　cout << "x1 = " << real1 << " + " << image1 << "j" << endl;

　　cout << "x2 = " << real2 << " + " << image2 << "j" << endl;

}

void main()

{

　　int a, b, c;

　　double temp;

　　cout << "输入a,b,c 的值" << endl;

　　cin >> a >> b >> c;

　　cout << "方程为：" << a << "x*x+" << b << "x+" << c << " = 0" << endl;

　　temp = b*b - 4 * a * c;

　　if (temp > 0)

　　　　equation_1(a, b, c);

　　if (temp == 0)

　　　　equation_2(a, b, c);

　　if (temp < 0)

　　　　equation_3(a, b, c);

　　system("pause");

}

运行结果：