#include <stdio.h>
#include <math.h>
#define EPS 1.0e-5
#define n 4

int main(void){
int i,k;

double x[n],y[n];

double sum_xy=0,sum_x=0,sum_y=0,sum_x2=0;

double a=0,b=0;

for(i=0;i<n;i++){
printf("X座標を入力[%d]：",i);
scanf("%lf",&x[i]);
printf("Y座標を入力[%d]：",i);
scanf("%lf",&y[i]);
}

for(k=0;k<n;k++){
sum_xy+=x[k]*y[k];
sum_x+=x[k];
sum_y+=y[k];
sum_x2+=x[k]*x[k];
}

a=(sum_x2*sum_y-sum_xy*sum_x)/(n*sum_x2-sum_x*sum_x);
b=(n*sum_xy-sum_x*sum_y)/(n*sum_x2-sum_x*sum_x);

printf("直線ｙ＝(%g)＋(%g)x",a,b);

return 0;
}