三分求函数的最小值;
#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <algorithm>
#include <cmath>
using namespace std;
typedef long long ll;
int main()
{
ios::sync_with_stdio(false);
double a,b,c,x,y;
while(cin>>a>>b>>c>>x>>y){
double l = -200,r = 200;
double lm,rm,dl,dr;
while(r-l>1e-8){//控制精度
lm = l+(r-l)/3,rm=r-(r-l)/3;
dl = sqrt((lm-x)*(lm-x)+(a*lm*lm+b*lm+c-y)*(a*lm*lm+b*lm+c-y));
dr = sqrt((rm-x)*(rm-x)+(a*rm*rm+b*rm+c-y)*(a*rm*rm+b*rm+c-y));
if(dl < dr) r = rm;
//dl小于dr,则最小值一定在l和rm之间
else l = lm;
}
double d = sqrt((l-x)*(l-x)+(a*l*l+b*l+c-y)*(a*l*l+b*l+c-y));
printf("%.3f\n",d);
}
return 0;
}