练习：
编写函数求解一个二次项系数不为0的一元二次方程，要求在一个函数中得到根的数目、方程的解。规定函数头：void EquationRoots(double a, double b, double c, double &x1, double &x2, int *NumRoots)。在主函数中测试结果是否正确。
代码如下：

#include<iostream>
#include<math.h>
using namespace std；/*求解一元二次方程，得到解的值和根的个数*/
void EquationRoots(double a, double b, double c, double &x1, double &x2, int *NumRoots)
{double delt;delt = b*b - 4*a*c;if(delt < 0)*NumRoots = 0;else if(delt == 0){*NumRoots = 1;x1 = (-b + sqrt(delt)) /(2*a);x2 = (-b - sqrt(delt)) /(2*a);}else{*NumRoots = 2;x1 = (-b + sqrt(delt)) /(2*a);x2 = (-b - sqrt(delt)) /(2*a); }
}/*输出结果*/ 
void PrintEquations(double x1, double x2, int NumRoots)
{if(NumRoots == 0)cout<<"此方程无解！"<<endl;else if(NumRoots == 1)cout<<"此方程有两个相同的实数根：x1=x2="<<x1<<endl;elsecout<<"此方程有两个不同的实数根：x1="<<x1<<",x2="<<x2<<endl;
}int main()
{double a,b,c,x1,x2;int NumRoots;int *num;num = &NumRoots;/*三组测试结果*/ a = 1; b = 2; c = 1;EquationRoots(a,b,c,x1,x2,num);PrintEquations(x1,x2,NumRoots);a = 1; b = 2; c = 2;EquationRoots(a,b,c,x1,x2,num);PrintEquations(x1,x2,NumRoots);a = 2; b = 3; c = -1.5;EquationRoots(a,b,c,x1,x2,num);PrintEquations(x1,x2,NumRoots);return 0;
}

运行结果：