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 <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <ctime>
#include <cassert>
#include <iostream>
#include <cctype>
#include <sstream>
#include <string>
#include <list>
#include <vector>
#include <queue>
#include <set>
#include <map>
#include <utility>
#include <numeric>
#include <algorithm>
#include <bitset>
#include <complex>
#include <fstream>
using namespace std;
typedef long long ll;
const double EPS = 1e-9;
typedef vector<int> vint;
typedef pair<int, int> pint;
#define rep(i, n) REP(i, 0, n)
#define ALL(v) v.begin(), v.end()
#define MSG(a) cout << #a << " " << a << endl;
#define REP(i, x, n) for(int i = x; i < n; i++)
template<class T> T RoundOff(T a){ return int(a+.5-(a<0)); }
template<class T, class C> void chmax(T& a, C b){ if(a < b) a = b; }
template<class T, class C> void chmin(T& a, C b){ if(b < a) a = b; }
template<class T, class C> pair<T, C> mp(T a, C b){ return make_pair(a, b); }


struct P{ double x, y; };


int main()
{
	int n;
	cin >> n;
	
	rep(i, n)
	{
		vector<P> v(3);

		rep(i, 3)
			cin >> v[i].x >> v[i].y;

		double a = v[0].x - v[1].x;
		double b = v[0].y - v[1].y;
		double c = v[1].x - v[2].x;
		double d = v[1].y - v[2].y;

		double A = pow(v[1].x, 2.0) - pow(v[0].x, 2.0) + pow(v[1].y, 2.0) + pow(v[0].y, 2.0);
		double B = pow(v[2].x, 2.0) - pow(v[1].x, 2.0) + pow(v[2].y, 2.0) + pow(v[1].y, 2.0);

		double acbd = a * d - b * c;

		double l = -(A * d - B * b) / acbd / 2;
		double m = -(B * a - A * c) / acbd / 2;

		double r = sqrt(pow(l - v[0].x, 2.0) + pow(m - v[0].y, 2.0));

		printf("%.3f %.3f %.3f\n", l, m, r);
	}
}

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

int main(){
	int n;
	double x1, y1, x2, y2, x3, y3, m1, m2, m3, b1, b2, b3, px, py, r;
	double d[2], e[2], f[2];
	cin >> n;
	for(int i = 0; i < n; i++){
		cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3;
		d[0] = (x2 + x3) / 2;
		d[1] = (y2 + y3) / 2;
		e[0] = (x3 + x1) / 2;
		e[1] = (y3 + y1) / 2; int count = 0;
        for(int i = 0; i <= n; i++){
            if(num[i]){
                count++;
            }
        }
        cout << count << endl;
    }

		f[0] = (x1 + x2) / 2;
		f[1] = (y1 + y2) / 2;
		m1 = (y3 - y2) / (x3 - x2);
		m2 = (y1 - y3) / (x1 - x3);
		m3 = (y2 - y1) / (x2 - x1);
		b1 = d[1] + d[0] / m1;
		b2 = e[1] + e[0] / m2;
		b3 = f[1] + f[0] / m3;
		px = -(b1 - b2) / ((1 / m2) - (1 / m1));
		py = -(1 / m1) * px + b1;
		r = (double)sqrt((x1 - px) * (x1 - px) + (y1 - py) * (y1 - py));
		px = floor(1000 * (px + 0.0005)) / 1000;
		py = floor(1000 * (py + 0.0005)) / 1000;
		r = floor(1000 * (r + 0.0005)) / 1000;
		cout << fixed << setprecision(3) << px << " " <<  py << " " << r << endl;
	}
	return 0;
}

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

using namespace std;

float round(float val){return ((int)(val*1000+0.5)/1000.0);}

int main(void){
	int n;
	float x[3],y[3],a,b,c,d,X,Y,px,py;

	cin >> n;
	for(int i=0;i<n;i++){
		for(int j=0;j<3;j++)
			cin >> x[j] >> y[j];

		a=x[0]-x[1];
		b=y[0]-y[1];
		c=x[0]-x[2];
		d=y[0]-y[2];
		X=pow(x[0],2)-pow(x[1],2)+pow(y[0],2)-pow(y[1],2);
		Y=pow(x[0],2)-pow(x[2],2)+pow(y[0],2)-pow(y[2],2);
		px=(d*X-b*Y)/(a*d-b*c)/2;
		py=(-c*X+a*Y)/(a*d-b*c)/2;

		printf("%.3f %.3f %.3f\n",round(px),round(py),round(sqrt(pow(x[0]-px,2)+pow(y[0]-py,2))));
	}
	return 0;
}

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

//line is ax + by = c
struct Line{
  double a, b, c;
};

struct Node{
  double x, y;
};

Line perpendicular_bisector(Node a, Node b){
  Line result;
  result.a = a.x - b.x;
  result.b = a.y - b.y;
  result.c = (a.x * a.x - b.x * b.x + a.y * a.y - b.y * b.y) / 2;
  return result;
}

Node intersection(Line l, Line m){
  Node result;
  result.x = (m.b * l.c - l.b * m.c) / (l.a * m.b - m.a * l.b);
  result.y = (m.a * l.c - l.a * m.c) / (m.a * l.b - l.a * m.b);
  return result;
}

double distance(Node a, Node b){
  return sqrt((a.x - b.x) * (a.x - b.x) + (a.y - b.y) * (a.y - b.y));
}

void solve(){
  Node A, B, C;
  cin >> A.x >> A.y;
  cin >> B.x >> B.y;
  cin >> C.x >> C.y;
  Line l = perpendicular_bisector(A, B);
  Line m = perpendicular_bisector(A, C);
  Node center = intersection(l, m);
  double raidus = distance(center, A);
  printf("%.3lf %.3lf %.3lf", center.x, center.y, raidus);
}

int main(){
  int N;
  cin >> N;
  while(N--){
    solve();
  }
}