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 <stdio.h>
#include <math.h>
 
int main()
{
    int n;
    double x1, x2, x3, y1, y2, y3, r, Px, Py;
    
    scanf("%d", &n);
    for(int i = 0; i < n; i++)
    {
        scanf("%lf %lf %lf %lf %lf %lf", &x1, &y1, &x2, &y2, &x3, &y3);
        Px = ((y2-y3)*(x1*x1+y1*y1) + (y3-y1)*(x2*x2+y2*y2) + (y1-y2)*(x3*x3+y3*y3))/(2*(x1*(y2-y3)+x2*(y3-y1)+x3*(y1-y2)));
        Py = ((x2-x3)*(x1*x1+y1*y1) + (x3-x1)*(x2*x2+y2*y2) + (x1-x2)*(x3*x3+y3*y3))/(2*(y1*(x2-x3)+y2*(x3-x1)+y3*(x1-x2)));
        r = sqrt((x1-Px)*(x1-Px)+(y1-Py)*(y1-Py));
        printf("%.3lf %.3lf %.3lf\n",Px, Py, r);
    }
    return 0;
}

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

int main(){
	int n;
	double x1, y1, x2, y2, x3, y3;

	cin >> n;
	for(int i = 0; i < n; i++){
		cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3;

		if(y1-y2==0.0 || y1-y3==0.0){
			swap(x1, x2);
			swap(y1, y2);
		}
		if(y1-y2==0.0 || y1-y3==0.0){
			swap(x1, x3);
			swap(y1, y3);
		}

		double a12, b12, a13, b13;
		a12 = -(x1-x2)/(y1-y2);
		a13 = -(x1-x3)/(y1-y3);

		double x12, y12, x13, y13;
		x12 = (x1+x2)/2.0;
		y12 = (y1+y2)/2.0;
		x13 = (x1+x3)/2.0;
		y13 = (y1+y3)/2.0;

		b12 = y12 - a12 * x12;
		b13 = y13 - a13 * x13;

		double xp, yp;
		xp = -(b12-b13)/(a12-a13);
		yp = a12*xp + b12;

		double r;
		r = sqrt(pow((x1-xp),2.0) + pow((y1-yp),2.0));

		printf("%.3f %.3f %.3f\n", xp, yp, r);
	}


	return(0);
}

C++: #include <iostream>
#include <cmath>
#include <algorithm>
#include <string>
#include <stdio.h>
using namespace std;
int main(){
    int n;
    cin >> n;
    for(int i=0;i<n;i++){
    double x1,y1,x2,y2,x3,y3;
    cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3;
    double x,y,r1,r;
    double a,b,c,d,e,f;
    a=2*x1-2*x2;
    b=2*y1-2*y2;
    c=x1*x1-x2*x2+y1*y1-y2*y2;
    d=2*x2-2*x3;
    e=2*y2-2*y3;
    f=x2*x2-x3*x3+y2*y2-y3*y3;
        x=(b*f-e*c)/(a*e-d*b);
        y=(c*d-f*a)/(a*e-d*b);
        
    r1=(x1-x)*(x1-x)+(y1-y)*(y1-y);
        r=sqrt(r1);
    
    printf("%.3f %.3f %.3f\n",x,y,r);
}
}

C++: #include <iostream>
#include <stdio.h>
#include <math.h>
using namespace std;
#define ep 0.00001

int main()
{
	double a, b, c, d, p, q;
	double x1, y1, x2, y2, x3, y3;
	double x, y, r;
	double det;
	int n;
	
	/*
	(x - x1)^2 + (y - y1)^2 = (x - x3)^2 + (y - y3)^2
	(x - x2)^2 + (y - y2)^2 = (x - x3)^2 + (y - y3)^2
	
	2(x3 - x1)x + 2(y3 - y1)y = (x3)^2 + (y3)^2 - (x1)^2 - (y1)^2
	2(x3 - x2)x + 2(y3 - y2)y = (x3)^2 + (y3)^2 - (x2)^2 - (y2)^2
	*/
	
	cin >> n;
	for (int i = 0; i < n; i++) {
		cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3;
		a = 2 * (x3 - x1);
		b = 2 * (y3 - y1);
		c = 2 * (x3 - x2);
		d = 2 * (y3 - y2);
		p = x3 * x3 + y3 * y3 - x1 * x1 - y1 * y1;
		q = x3 * x3 + y3 * y3 - x2 * x2 - y2 * y2;
		
		det = a * d - b * c;
		x = (d * p - b * q) / det + ep;
		y = (a * q - c * p) / det + ep;
		
		r = hypot(x - x1, y - y1);
		printf("%.3f %.3f %.3f\n", x, y, r);
	}
	return 0;
}

C++: #include <iomanip>
#include <iostream>
#include <vector>
#include <string>
#include <map>
#include <algorithm>
#include <complex>

#define REP(i,n) for(int i=0;i<(int)(n);i++)

using namespace std;

typedef long double ld;
typedef complex<ld> P;
typedef vector<P> VP;
const ld eps = 1e-8, pi = acos(-1.0);

#define EQ(a,b) (abs((a)-(b))<eps)

class C { public: P p; ld r; };

ld dot (P a, P b) { return real(conj(a) * b); }
ld cross (P a, P b) { return imag(conj(a) * b); }

VP is_cc(C c1, C c2){
  VP res;
  ld d = abs(c1.p - c2.p);
  ld rc = (d * d + c1.r * c1.r - c2.r * c2.r) / (2 * d);
  ld dfr = c1.r * c1.r - rc * rc;
  if (abs(dfr) < eps) dfr = 0.0;
  else if (dfr < 0.0) return res; // no intersection
  ld rs = sqrt(dfr);
  P diff = (c2.p-c1.p)/d;
  res.push_back(c1.p + diff * P(rc, rs));
  if (dfr != 0.0) res.push_back(c1.p + diff * P(rc, -rs));
  return res;
}

ld circumradius(VP tri) {
  P x = tri[1] - tri[0];
  P y = tri[2] - tri[0];
  ld sxy = cross(x,y)/abs(x)/abs(y);
  return abs(x-y)/sxy/2;
}

P circumcenter(VP tri) {
  ld r = circumradius(tri);
  C c0 = {tri[0], r};
  C c1 = {tri[1], r};
  VP vcc = is_cc(c0, c1);
  if (abs(abs(vcc[0] - tri[2]) - r) < eps) return vcc[0];
  return vcc[1];
}

int main() {
  int n;
  cin>>n;
  REP(i,n) {
    VP p(3);
    REP(j,3) {
      ld x,y;
      cin>>x>>y;
      p[j] = P(x,y);
    }
    P cc = circumcenter(p);
    ld r = circumradius(p);
    cout<<setprecision(3)<<fixed<<real(cc)<<' '<<imag(cc)<<' '<<r<<endl;
  }
  return 0;
}