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 <iomanip>
#include <cmath>

using namespace std;

void calcInverseMatrix(double A[][3], double invA[][3]);

int main(void)
{
	int n = 0;
	cin >> n;
	
	for(int i = 0; i < n; i++){
		double x1 = 0.0, y1 = 0.0;
		double x2 = 0.0, y2 = 0.0;
		double x3 = 0.0, y3 = 0.0;
		cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3;
		
		double A[3][3] = {0};
		double invA[3][3] = {0};
		
		A[0][0] = x1;
		A[0][1] = y1;
		A[0][2] = 1.0;
		A[1][0] = x2;
		A[1][1] = y2;
		A[1][2] = 1.0;
		A[2][0] = x3;
		A[2][1] = y3;
		A[2][2] = 1.0;
		
		calcInverseMatrix(A, invA);
		
		double B[3] = {0};
		B[0] = - x1 * x1 - y1 * y1;
		B[1] = - x2 * x2 - y2 * y2;
		B[2] = - x3 * x3 - y3 * y3;
		
		double C[3] = {0};
		for(int i = 0; i < 3; i++){
			C[i] = invA[i][0]*B[0] + invA[i][1]*B[1] + invA[i][2]*B[2];
		}
		
		double centX = - C[0] / 2.0;
		double centY = - C[1] / 2.0;
		double radius = sqrt(centX * centX + centY * centY - C[2] * C[2]);
		cout << showpoint << setprecision(4) << centX << " " << centY << " " << radius << endl;
	}
	
	return 0;
}

void calcInverseMatrix(double A[][3], double invA[][3])
{
	double det = A[0][0]*A[1][1]*A[2][2] + A[1][0]*A[2][1]*A[0][2] +
				 A[2][0]*A[0][1]*A[1][2] - A[0][0]*A[2][1]*A[1][2] -
				 A[2][0]*A[1][1]*A[0][2] - A[1][0]*A[0][1]*A[2][2];
	
	invA[0][0] = (A[1][1]*A[2][2] - A[1][2]*A[2][1]) / det;
	invA[0][1] = (A[0][2]*A[2][1] - A[0][1]*A[2][2]) / det;
	invA[0][2] = (A[0][1]*A[1][2] - A[0][2]*A[1][1]) / det;
	invA[1][0] = (A[1][2]*A[2][0] - A[1][0]*A[2][2]) / det;
	invA[1][1] = (A[0][0]*A[2][2] - A[0][2]*A[2][0]) / det;
	invA[1][2] = (A[0][2]*A[1][0] - A[0][0]*A[1][2]) / det;
	invA[2][0] = (A[1][0]*A[2][1] - A[1][1]*A[2][0]) / det;
	invA[2][1] = (A[0][1]*A[2][0] - A[0][0]*A[2][1]) / det;
	invA[2][2] = (A[0][0]*A[1][1] - A[0][1]*A[1][0]) / det;
}

C++: #include <iostream>
#include <iomanip>
#include <math.h>
using namespace std;

int main(void){
    int n;
    long double x1, x2, x3, y1, y2, y3, Px, Py, r;
    cin >> n;
    
    for(int i=1; i<=n; i++){
        cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3;
    
        Px = ( (x1*x1 + y1*y1 - x3*x3 - y3*y3) / (2 * (y1-y3)) - (x2*x2 + y2*y2 - x3*x3 - y3*y3) / (2 * (y2-y3)) ) / ( (x1-x3)/(y1-y3) - (x2-x3)/(y2-y3) );
        Py = -(x1-x3) / (y1-y3) * Px + (x1*x1 + y1*y1 - x3*x3 - y3*y3) / (2 * (y1-y3));
        
        r = sqrt((x1-Px)*(x1-Px) + (y1-Py)*(y1-Py));

        cout << fixed << setprecision(3) << Px << " " << Py << " " << r << endl;
    }
    return 0;
}

C++: #define _USE_MATH_DEFINES
#include <bits/stdc++.h>
#define int long long
#define rep(i,n) for(int i=0;i<n;i++)
#define Rep(i,a,b) for(int i=a;i<b;i++)
#define REP(i,a,b) for(int i=a;i<=b;i++)
#define rev(i,n) for(int i=n-1;i>=0;i--)
#define vi vector<int>
#define vvi vector<vi>
#define pb push_back
#define pi pair<int,int>
#define vp vector<pair<int,int>>
#define mp make_pair
#define all(v) (v).begin(),(v).end()
#define fi first
#define se second
#define MEMSET(a) memset(a,0,sizeof(a))
#define inf (1ll<<60)
#define Yes(f) cout<<(f?"Yes":"No")<<endl
#define yes(f) cout<<(f?"yes":"no")<<endl
#define YES(f) cout<<(f?"YES":"NO")<<endl
#define SORT(v) sort(all(v))
#define RSORT(v) sort(all(v), greater<int>())
#define VI(a,n) vi a(n); rep(i,n)cin>>a[i];
#define sq(n) (n)*(n)

using namespace std;

const int mod=1e9+7;

void run();

void init() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout<<fixed<<setprecision(3);
}

signed main(){
    init();
    run();
    return 0;
}

void run(){
    int n;
    cin>>n;
    while(n--){
        double x1,x2,x3,y1,y2,y3;
        cin>>x1>>y1>>x2>>y2>>x3>>y3;
        double a=2*(x2-x1),b=2*(y2-y1),c=sq(x2)-sq(x1)+sq(y2)-sq(y1);
        double d=2*(x3-x2),e=2*(y3-y2),f=sq(x3)-sq(x2)+sq(y3)-sq(y2);
        double x=(c*e-b*f)/(a*e-b*d);
        double y=(c*d-a*f)/(b*d-a*e);
        if(x==-0)x=0;
        if(y==-0)y=0;
        double r=sqrt(sq(x-x1)+sq(y-y1));
        cout<<x<<" "<<y<<" "<<r<<endl;
    }
}