一元二次方程.cpp

一元二次方程求解

//方程
#include<cmath>//定义sqrt()函数
#include<iostream>
using namespace std;
int main()
{
	float a,b,c;
	cout<<"Enter the coefficients of a quadratic equation:"<<endl;
	cin>>a>>b>>c;
	if (fabs(a)<=1e-6) 
	{
		cout<<"This is not a quadratic equation: a==0\n";
		return 0;
	}
	else
	    cout<<"The equation is:"<<a<<"*x*x+"<<b
		    <<"*x+"<<c<<"=0"<<endl;
	double d=b*b-4*a*c;//判别式
	if (fabs(d)<=1e-6) 
	{
		cout<<"This equation has no real solutions: d<0\n";
		return 0;
	}
	else
       //double sqrtd=sqrt(d);
	   double x1=(-b+sqrt(d))/(2*a);
	   double x2=(-b-sqrt(d))/(2*a);
	   cout<<"The solution are:"<<endl;
	   cout<<"x1="<<x1<<endl;
	   cout<<"x2="<<x2<<endl;
	   cout<<"check:"<<endl;
	   cout<<"\ta*x1*x1+b*x1+c="<<a*x1*x1+b*x1+c<<endl;
	   cout<<"\ta*x2*x2+b*x2+c="<<a*x2*x2+b*x2+c<<endl;
	   return 0;
}