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 <stdio.h>
#include <string>
#include <queue>
#include <cmath>

#define int64 long long int

using namespace std;

double round(double x){
	if(x > 0) return floor(x + 0.5);
	else return -1.0 * floor(fabs(x) + 0.5);
}

int main()
{
	int n;
	double x1,y1,x2,y2,x3,y3,x,y,r;
	double det,a1,b1,a2,b2,c1,c2;
	cin >> n;
	for(int i=0; i<n; i++){
		cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3;
		a1 = 2 * (x1 - x2), b1 = 2 * (y1 - y2);
		a2 = 2 * (x2 - x3), b2 = 2 * (y2 - y3);
		det = a1 * b2 - a2 * b1;
		c1 = (x1*x1 - x2*x2) + (y1*y1 - y2*y2);
		c2 = (x2*x2 - x3*x3) + (y2*y2 - y3*y3);
		x = (a1 * c1 + b1 * c2) / det;
		y = (a2 * c1 + b2 * c2) / det;
		r = sqrt((x - x1)*(x - x1) + (y - y1)*(y - y1));
		x *= 1000, y *= 1000, r *= 1000;
		x = round(x), y = round(y), r = round(r);
		x /= 1000, y /= 1000, r /= 1000;
		if(fabs(x) < 1e-6) x = 0.0;
		if(fabs(y) < 1e-6) y = 0.0;
		printf("%.3f %.3f %.3f\n", x, y, r);
	}
	return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;

int main()
{
  int n;

  cin >> n;
  while (n--){
    double x1, x2, x3, y1, y2, y3;
    cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3;

    double a1 = 2 * (x2 - x1);
    double b1 = 2 * (y2 - y1);
    double c1 = x1 * x1 - x2 * x2 + y1 * y1 - y2 * y2;

    double a2 = 2 * (x3 - x1);
    double b2 = 2 * (y3 - y1);
    double c2 = x1 * x1 - x3 * x3 + y1 * y1 - y3 * y3;

    double x = (b1 * c2 - b2 * c1) / (a1 * b2 - a2 * b1);
    double y = (c1 * a2 - c2 * a1) / (a1 * b2 - a2 * b1);

    double r = hypot(x - x1, y - y1);

    printf("%.3f %.3f %.3f\n", x, y, r);
  }
}

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

#define pow2(x) ((x)*(x))

int main() {
	double x0, y0, x1, y1, X0, Y0, X1, Y1;
	double a1, b1, a2, b2, a3, b3;
	int n;
	cin >> n;
	while(n--) {
		cin >> a1 >> b1 >> a2 >> b2 >> a3 >> b3;
		x0 = (a1 + a2) / 2.0; y0 = (b1 + b2) / 2.0;
		x1 = -(b2 - b1); y1 = (a2 - a1);
		X0 = (a2 + a3) / 2.0; Y0 = (b2 + b3) / 2.0;
		X1 = -(b3 - b2); Y1 = (a3 - a2);
		double s = (Y1*(x0 - X0) - X1*(y0 - Y0)) / (X1*y1 - Y1*x1);
		double p = x0 + s * x1, q = y0 + s * y1;
		double r = sqrt(pow2(p - a1) + pow2(q - b1));
		printf("%.3f %.3f %.3f\n", p, q, r);
	}
	return 0;
}

C++: #include "bits/stdc++.h"
using namespace std;
#define SQ(x) ((x) * (x))
typedef long long ll;
typedef pair<int, int> pii;

#define FOR(i, s, e) for (int(i) = (s); (i) < (e); (i)++)
#define debug(x) cout << #x << ": " << x << endl
#define ALL(x) (x).begin(),(x).end()

const int INF = 1e9;
const ll LINF = 1e16;

int main() {
	cin.tie(0);
	ios_base::sync_with_stdio(false);
	int s;
	int i;
	double x1, x2, x3;
	double y1, y2, y3;
	double a, b, c, d, e, f;
	double l, m, n;

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

		a = (x1 - x2);
		b = (y1 - y2);
		c = -1 * (SQ(x1) - SQ(x2) + SQ(y1) - SQ(y2));
		d = (x1 - x3);
		e = (y1 - y3);
		f = -1 * (SQ(x1) - SQ(x3) + SQ(y1) - SQ(y3));

		l = (c * e - b * f) / (e * a - b * d);
		m = (d * c - a * f) / (d * b - e * a);

		n = -1 * (SQ(x1) + SQ(y1) + l * x1 + m * y1);

		printf("%.3f %.3f %.3f\n", l / -2.0, m / -2.0, sqrt(SQ(l) + SQ(m) - 4 * n) / 2.0);
	}

	return (0);
}