C++ :

#include <stdio.h>

int t,a,b;

int main(){
    //freopen("input.in","r",stdin);
    //freopen("input.out","w",stdout);
    scanf("%d",&t);
    while(t--){
        scanf("%d%d",&a,&b);
        if(a == b){
            puts("no");
            continue;
        }
        double a1 = a*1.0*a/b/b;
        double q = (2.0*a*b)/(a*1.0*a + b*1.0*b);
        printf("%.4lf\n",a1 / (1-q));
    }
    return 0;
}