編寫一個求方程ax^2+bx+c=0的根的程序，用3個函數分別求當b^2-4ac大於零、等於零和小於零時的方程的根。要求從主函數輸入a、b、c的值並輸出結果-簡單

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 << "兩個不相等的實根" << 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 << "兩個相等的實根" << 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 << "兩個虛根" << endl;

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

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

}

void main()

{

　　int a, b, c;

　　double temp;

　　cout << "輸入a,b,c 的值" << endl;

　　cin >> a >> b >> c;

　　cout << "方程為：" << 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");

}

運行結果：