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 <cmath>

using namespace std;

struct point{
    double x;
    double y;
};

int main(){
    int n;
    struct point points[3];

    cin>>n;
    for (int j = 0; j < n; ++j) {
        double s,a,b,c;
        for (int i = 0; i < 3; ++i) {
            cin >> points[i].x >> points[i].y;
        }
        a  = sqrt(pow(points[0].x-points[1].x,2)+pow(points[0].y-points[1].y,2));
        b  = sqrt(pow(points[1].x-points[2].x,2)+pow(points[1].y-points[2].y,2));
        c  = sqrt(pow(points[2].x-points[0].x,2)+pow(points[2].y-points[0].y,2));
        s  = (a+b+c)/2;
        printf("%.3f %.3f %.3f\n",
               ((points[0].y - points[2].y)*(pow(points[0].y,2) - pow(points[1].y,2) + pow(points[0].x,2) - pow(points[1].x,2)) - (points[0].y - points[1].y)*(pow(points[0].y,2) - pow(points[2].y,2) + pow(points[0].x,2) - pow(points[2].x,2))) / (2*(points[0].y - points[2].y)*(points[0].x - points[1].x) - 2*(points[0].y - points[1].y)*(points[0].x - points[2].x))+5e-5,
               ((points[0].x - points[2].x)*(pow(points[0].x,2) - pow(points[1].x,2) + pow(points[0].y,2) - pow(points[1].y,2)) - (points[0].x - points[1].x)*(pow(points[0].x,2) - pow(points[2].x,2) + pow(points[0].y,2) - pow(points[2].y,2))) / (2*(points[0].x - points[2].x)*(points[0].y - points[1].y) - 2*(points[0].x - points[1].x)*(points[0].y - points[2].y))+5e-5,
               a*b*c/(4*sqrt(s*(s-a)*(s-b)*(s-c)))+5e-5
        );
    }
    return 0;
}

C++: #include <iostream>
#include <sstream>
#include <string>
#include <vector>
#include <stack>
#include <queue>
#include <set>
#include <map>
#include <algorithm>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cctype>
#include <cmath>
#include <cassert>

using namespace std;

#define all(c) ((c).begin()), ((c).end())
#define debug(c) cerr << "> " << #c << " = " << (c) << endl;
#define iter(c) __typeof((c).begin())
#define tr(i, c) for (iter(c) i = (c).begin(); i != (c).end(); i++)
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define REP(i, a, b) for (int i = (int)(a); i <= (int)(b); i++)

#define mp make_pair
#define fst first
#define snd second
#define pb push_back


const double EPS = 1e-10;


typedef long long ll;
typedef vector<int> vi;
typedef pair<int, int> pii;
typedef complex<double> P;


inline double inp(const P &a, const P &b) {
	return (conj(a) * b).real();
}

inline double outp(const P &a, const P &b) {
	return (conj(a) * b).imag();
}

P circumc(const P &a, const P &b, const P &c) {
	return (a + b - (inp(c - b, a - c) / outp(b - a, c - b)) * (b - a) * P(0, 1)) / 2.0;
}

int main(){
	int n; cin >> n;
	while (n--) {
		double x1, y1, x2, y2, x3, y3; cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3;
		P p1(x1, y1), p2(x2, y2), p3(x3, y3);
		P c = circumc(p1, p2, p3);
		printf("%.3f %.3f %.3f\n", c.real(), c.imag(), abs(p1 - c));
	}
	return 0;
}