>>547

できた
#include<stdio.h>

int main(){
double x[]={20.0,40.0,60.0,80.0,100.0};
double y[]={1.31,2.93,3.21,4.85,5.46};
double a,b;
int i,j,n;
double xk,yk,xy,x2;
FILE *fp;
xk=yk=xy=x2=0;
a = 0;
b = 0;
n=5;
fp = fopen("test.dat","w");
for(i=0;i<n;i++){
xk += x[i];
yk += y[i];
xy += x[i]*y[i];
x2 += x[i]*x[i];
fprintf(fp,"%f %f¥n",x[i],y[i]);
}
printf("%lf %lf %lf %lf¥n",xk,yk,xy,x2);
a = (n*xy - xk*yk)/(n*x2 - xk*xk);
b = (x2*yk - xy*xk)/(n*x2 - xk*xk);
printf("f(x) = %lf * x + %lf¥n",a,b);
return 0;
}
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