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>
#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;
		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;
		double vx12, vy12, vx13, vy13;
		vx12 = x2-x1;
		vy12 = y2-y1;
		vx13 = x3-x1;
		vy13 = y3-y1;
		double x, y;
		x = (vx12*vy13*x12-vx13*vy12*x13+vy12*vy13*(y13-y12))/(vx12*vy13-vx13*vy12);
		y = y13 - vx13*(x-x13)/vy13;
		double r;
		r = sqrt((x-x1)*(x-x1)+(y-y1)*(y-y1));
		printf("%.3f %.3f %.3f\n", x, y, r);
	}
	return 0;
}

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

int main()
{
        int n;
        double a,b,c,d,e,f;
        double x1,x2,x3,y1,y2,y3;
        double px,py;
        double r;

        cin >> n;

        for(int i=0;i<n;i++){
                cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3;
                a = (x2-x1)*2.0;
                b = (y2-y1)*2.0;
                c = (x2*x2 + y2*y2 - x1*x1 - y1*y1);
                d = (x3-x1)*2.0;
                e = (y3-y1)*2.0;
                f = (x3*x3 + y3*y3 - x1*x1 - y1*y1);
                px = (c*e-b*f)/(a*e-b*d);
                py = (a*f-c*d)/(a*e-b*d);
                r = sqrt((px-x1)*(px-x1) + (py-y1)*(py-y1));
                printf("%.3f %.3f %.3f\n",px,py,r);



        }

        return 0;
}

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

using namespace std;

int main()
{
    int num;
    cin >> num;
    double x1, x2, x3, y1, y2, y3;
    double px, py, r;

    for(int i = 0; i < num; ++i)
    {
        cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3;
        px = (1 / 2.0) * ((x1 * x1 + y1 * y1) * (y3 - y2) + (x2 * x2 + y2 * y2) * (y1 - y3)
            + (x3 * x3 + y3 * y3) * (y2 - y1)) / (x1 * (y3 - y1) + x2 * (y1 - y3) + x3 * (y2 - y1));
        py = -(x3 - x2) / (y3 - y2) * px + (1 / 2.0) * (x3 * x3 - x2 * x2 + y3 * y3 - y2 * y2) / (y3 - y2);
        r = sqrt((x1 - px) * (x1 - px) + (y1 - py) * (y1 - py));

        cout << fixed << setprecision(3) << px << " " << py << " " << r << endl;
    }
}

C++: #include<iostream>
#include<string>
#include <iomanip>
using namespace std;
int main() {
	int n;
	cin >> n;
	float x1, y1, x2, y2, x3, y3;
	cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3;

	float px, py, r;
	float A1, B1, C1, A2, B2, C2;
	A1 = 2 * (x2 - y2);
	B1 = 2*(y2 - y1);
	C1 = x1*x1 - x2*x2 + y1*y1 - y2*y2;
	A2 = 2 * (x3 - x1);
	B2 = 2 * (y3 - y1);
	C2 = x1*x1 - x3*x3 + y1*y1 - y3*y3;
	
	px = (B1*C2 - B2*C1) / (A1*B2 - A2*B1);
	py = (C1*A2 - C2*A1) / (A1*B2 - A2*B1);

	r = sqrt((x1-px)*(x1-px)+(y1-py)*(y1-py));

	px = round(px * 1000) / 1000;
	py = round(py * 1000) / 1000;
	r = round(r * 1000) / 1000;
	cout <<fixed << setprecision(4) << px << " ";
	cout << fixed << setprecision(4) << py << " ";
	cout<< fixed << setprecision(4) << r << endl;

	return 0;

}