Go: package main

import (
	"bufio"
	"fmt"
	"io"
	"math"
	"os"
	"strconv"
	"strings"

)


func main() {
	solve(os.Stdin, os.Stdout)
}

type ReaderEx struct {
	baseScanner *bufio.Scanner
	words       []string
	nextWordIdx func() int
	initWordIdx func(int)
}

func NewScannerEx(stdin io.Reader) *ReaderEx {
	var this ReaderEx
	var idx int
	var wordsCnt int
	this.baseScanner = bufio.NewScanner(stdin)
	this.baseScanner.Buffer(make([]byte, 0), 1E+11)
	this.nextWordIdx = func() int {
		cur := idx
		idx = (idx + 1) % wordsCnt
		return cur
	}
	this.initWordIdx = func(wc int) {
		idx = 0
		wordsCnt = wc
	}
	return &this
}

func (me *ReaderEx) Scan(doSplit bool) (isScanned bool) {
	isScanned = me.baseScanner.Scan()
	if doSplit {
		me.words = strings.Fields(me.baseScanner.Text())
	} else {
		me.words = []string{me.baseScanner.Text()}
	}
	me.initWordIdx(len(me.words))
	return
}

func (me *ReaderEx) nextBytes() []byte {
	return []byte(me.words[me.nextWordIdx()])
}
func (me *ReaderEx) nextString() string {
	return me.words[me.nextWordIdx()]
}

type StringArray []string

func (me *ReaderEx) nextStringArray() StringArray {
	return me.words[me.nextWordIdx():]
}

func (me StringArray) toStrings() []string {
	return me
}

func (me StringArray) toInts() []int {
	strValues := me.toStrings()
	values := make([]int, len(strValues))
	for i, v := range strValues {
		n, err := strconv.Atoi(v)
		if err != nil {
			panic(err)
		}
		values[i] = n
	}
	return values
}
func (me *ReaderEx) nextInt() int {
	n, err := strconv.Atoi(me.words[me.nextWordIdx()])

	defer func() {
		if err != nil {
			panic(fmt.Sprintf("getInt(%d)", n))
		}
	}()
	return n
}

func pow(x, y, mod int) (ans int) {

	ans = 1
	for bit := 1 << uint(math.Floor(math.Log2(float64(y)))); ; bit >>= 1 {
		if y&bit != 0 {
			ans *= x
			if mod > 0 {
				ans %= mod
			}
		}
		if bit <= 1 {
			return
		}
		ans *= ans
		if mod > 0 {
			ans %= mod
		}
	}
}

type factType struct {
	prime int
	count int
}

func fact(n int) (facts []*factType) {

	for i := 2; i*i <= n; i++ {
		if n%i == 0 {
			fa := factType{prime: i}
			for n%fa.prime == 0 {
				n /= fa.prime
				fa.count++
			}
			facts = append(facts, &fa)
		}
	}
	if n > 1 {
		facts = append(facts, &factType{prime: n, count: 1})
	}
	return facts
}
func dec2bin(n int) (ret []bool) {
	for bit := 1 << uint(math.Floor(math.Log2(float64(n)))); ; bit >>= 1 {
		ret = append(ret, n&bit != 0)

		if bit <= 1 {
			return
		}
	}

}

func abs(v int) int {
	if v < 0 {
		v = -v
	}
	return v
}

func b2i(b bool) (i int) {
	if b {
		i = 1
	} else {
		i = 0
	}
	return
}

func solve(stdin io.Reader, stdout io.Writer) {

	r := NewScannerEx(stdin)
	r.Scan(true)
	n := r.nextInt()

	type Vec struct {
		x, y float64
	}
	vec := func(a, b Vec) Vec { return Vec{b.x - a.x, b.y - a.y} }
	unv := func(a Vec) Vec { return Vec{-a.y, a.x} }
	cdot := func(a, b Vec) float64 { return a.x*b.x + a.y*b.y }
	times := func(t float64, a Vec) Vec { return Vec{t * a.x, t * a.y} }
	add := func(a, b Vec) Vec { return Vec{a.x + b.x, a.y + b.y} }
	for i := 0; i < n; i++ {

		r.Scan(true)
		nextFloat64 := func() (ret float64) { fmt.Sscanf(r.nextString(), "%f", &ret); return }
		a1, a2, a3 := Vec{nextFloat64(), nextFloat64()}, Vec{nextFloat64(), nextFloat64()}, Vec{nextFloat64(), nextFloat64()}
		unv23 := unv(vec(a2, a3))
		v12 := vec(a1, a2)
		v31 := vec(a3, a1)
		s := cdot(v12, v31) / 2 / cdot(v12, unv23)
		c := add(times(.5, add(a2, a3)), times(s, unv23))
		v1c := vec(a1, c)
		fmt.Fprintf(stdout, "%.3f %.3f %.3f\n", c.x, c.y, math.Sqrt(v1c.x*v1c.x+v1c.y*v1c.y))
	}
}

C++: #include<iostream>
#include<vector>
#include<algorithm>
#include<cmath>
#include<cstdio>

using namespace std;

typedef double Real;

Real EPS = 1e-8;

int sgn(Real a, Real b=0){return a<b-EPS?-1:a>b+EPS?1:0;}
Real sqr(Real a){return sqrt(max(a,(Real)0));}

struct Point{
  Real add(Real a, Real b){
    if(abs(a+b) < EPS*(abs(a)+abs(b)))return 0;
    return a+b;
  }
  Real x, y;
  Point(){}
  Point(Real x,Real y) : x(x) , y(y){}

  Point operator + (Point p){return Point(add(x,p.x), add(y,p.y));}
  Point operator - (Point p){return Point(add(x,-p.x), add(y,-p.y));}
  Point operator * (Real d){return Point(x*d,y*d);}
  Point operator / (Real d){return Point(x/d,y/d);}
  Real norm(){return sqr(x*x+y*y);}
  Real dist(Point a){return (*this-a).norm();}
  Real dot(Point a){return x*a.x+y*a.y;}
  Real cross(Point a){return x*a.y-y*a.x;}
};

struct circle{
  Point p;
  Real r;
  circle(){}
  circle(Point p, Real r) : p(p) , r(r){}
};

circle circumscribed_circle(Point p, Point q, Point r){
  Point a,b,c;
  circle res;
  a=(q-p)*2;
  b=(r-p)*2;
  c.x=p.dot(p)-q.dot(q);  
  c.y=p.dot(p)-r.dot(r);

  res.p.x=a.y*c.y-b.y*c.x;
  res.p.y=b.x*c.x-a.x*c.y;
  res.p=res.p/a.cross(b);
  return circle(res.p, p.dist(res.p));
}

int main(void){
  int n;
  cin >> n;
  while(n--){
    vector<Point>v(3);
    for(int i=0;i<3;i++)
      cin >> v[i].x >> v[i].y;

    circle res=circumscribed_circle(v[0],v[1],v[2]);
    cout << res.p.x << " " << res.p.y << " " << res.r << endl;
  }
  
  return 0;
}

C++: #include<bits/stdc++.h>
#define rep(i,n)for(int i=0;i<(n);i++)
using namespace std;

int main() {
	int n; scanf("%d", &n);
	rep(i, n) {
		double x1, y1, x2, y2, x3, y3;
		cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3;
		double a = -x1 + x2, b = -y1 + y2, c = (-pow(x1, 2) - pow(y1, 2) + pow(x2, 2) + pow(y2, 2)) / 2;
		double d = -x1 + x3, e = -y1 + y3, f = (-pow(x1, 2) - pow(y1, 2) + pow(x3, 2) + pow(y3, 2)) / 2;
		double y = (c*d - a*f) / (b*d - a*e);
		string t = to_string(y);
		if (t == "inf")abort();
		double x = (c - b*y) / a;
		string s = to_string(x);
		if (s == "inf")abort();
		printf("%.3lf %.3lf %.3lf\n", x, y, hypot(x1 - x, y1 - y));
	}
}

C++: #include <iostream>
#include <math.h>

using namespace std;

int main(){
	int n;
	cin >> n;

	for(int i=0; i<n; i++){
		double x1, y1, x2, y2, x3, y3;
		double px, py, r;

		cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3;

		px = (x1 + x2 + x3) / 3;
		py = (y1 + y2 + y3) / 3;
		r = sqrt((x1-px)*(x1-px) + (y1-py)*(y1-py));

		printf("%.3f %.3f %.3f\n", px, py, r);
	}

	return 0;
}

C++: #include <iostream>
#include <cmath>
#include <iomanip>
using namespace std;

int list[1000000] = {};

int main(){
	cin.tie(0);
	ios::sync_with_stdio(false);
	
	int n;
	cin >> n;
	
	while(n-- > 0){
	
	double x1, y1, x2, y2, x3, y3;
	cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3;
	
	double a = 2 * (x2 - x1);
	double b = 2 * (y2 - y1);
	double c = x1 * x1 - x2 * x2 + y1 * y1 - y2 * y2;
	double d = 2 * (x3 - x2);
	double e = 2 * (y3 - y2);
	double f = x2 * x2 - x3 * x3 + y2 * y2 - y3 * y3;
		
	double cx = (b * f - c * e)/(a * e - d * b);
	double cy = (a * f - c * d)/(b * d - a * e);
		
	double r = sqrt((x1 - cx)*(x1 - cx) + (y1 - cy)*(y1 - cy));
	
	cout << fixed << cx << " " << cy << " " << r << endl;
	
	}
	
	return 0;
}

C++: #include<iostream>
#include<cmath>
#include<cstdio>
using namespace std;
int main(){
	double a[2],b[2],c[2];
	double matrix[2][2],ans[2],reverse[2][2],det;
	double r,o[2];
	int n;
	cin >>n;
	for(int i=0; i<n; i++){
		cin >>a[0]>>a[1]>>b[0]>>b[1]>>c[0]>>c[1];
		b[0] = b[0]-a[0];
		b[1] = b[1]-a[1];
		c[0] = c[0]-a[0];
		c[1] = c[1]-a[1];
		matrix[0][0] = 2*b[0];
		matrix[1][0] = 2*b[1];
		matrix[0][1] = 2*c[0];
		matrix[1][1] = 2*c[1];
		ans[0] = b[0]*b[0]+b[1]*b[1];
		ans[1] = c[0]*c[0]+c[1]*c[1];
		det = matrix[0][0]*matrix[1][1]-matrix[0][1]*matrix[1][0];
		reverse[0][0] = matrix[1][1]/det;
		reverse[1][0] = -matrix[1][0]/det;
		reverse[0][1] = -matrix[0][1]/det;
		reverse[1][1] = matrix[0][0]/det;
		o[0] = ans[0]*reverse[0][0]+ans[1]*reverse[1][0];
		o[1] = ans[0]*reverse[0][1]+ans[1]*reverse[1][1];
		r = sqrt(o[0]*o[0]+o[1]*o[1]);
		o[0]+=a[0];
		o[1]+=a[1];
		printf("%.3lf %.3lf %.3lf",o[0],o[1],r);
	}
	return 0;
}