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 <vector>
#include <map>
#include <set>
#include <stack>
#include <queue>
#include <algorithm>
#include <numeric>
#include <utility>
#include <sstream>
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <string>
#include <cstring>
#include <complex>
#include <ctime>
#include <cstdlib>

using namespace std;

inline int to_int(string s) {int v; istringstream sin(s); sin >> v; return v;}
template<class T> inline string to_str(T x) {ostringstream sout; sout << x; return sout.str();}

typedef long long ll;

int main()
{
	double x1, y1, x2, y2, x3, y3;
	double a1, b1, c1, a2, b2, c2;
	double ansx, ansy, ansr;
	int n;
	cin >> n;

	while(n--)
	{
		cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3;
		a1 = 2 * (x2 - x1);
		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;
		ansx = (b1*c2 - b2*c1)/(a1*b2 - a2*b1);
		ansy = (c1*a2 - c2*a1)/(a1*b2 - a2*b1);
		ansr = sqrt( (x1-ansx)*(x1-ansx) + (y1-ansy)*(y1-ansy) );
		printf("%.3f %.3f %.3f\n", ansx, ansy, ansr);
	}
}

C++: #include <iostream>
#include <sstream>
#include <string>
#include <vector>
#include <deque>
#include <stack>
#include <queue>
#include <set>
#include <map>
#include <bitset>
#include <algorithm>
#include <numeric>
#include <complex>
#include <functional>
#include <utility>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>

using namespace std;

#define dump(n) cout<<"# "<<#n<<"="<<(n)<<endl
#define debug(n) cout<<__FILE__<<","<<__LINE__<<": #"<<#n<<"="<<(n)<<endl
#define repi(i,a,b) for(int i=int(a);i<int(b);i++)
#define rep(i,n) repi(i,0,n)
#define iter(c) __typeof((c).begin())
#define tr(c,i) for(iter(c) i=(c).begin();i!=(c).end();i++)
#define allof(c) (c).begin(),(c).end()
#define mp make_pair

typedef long long ll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<string> vs;
typedef pair<int,int> pii;

pair<double,double> solve(double a,double b,double c,double d,double e,double f)
{
	return mp((c*e-b*f)/(a*e-b*d),(a*f-c*d)/(a*e-b*d));
}

int main()
{
	int n;
	cin>>n;
	rep(i,n){
		vector<double> x(3),y(3);
		rep(j,3)
			cin>>x[j]>>y[j];
		double x0=x[0],y0=y[0];
		rep(j,3){
			x[j]-=x0;
			y[j]-=y0;
		}
		pair<double,double> res=solve(
			2*x[1],2*y[1],x[1]*x[1]+y[1]*y[1],
			2*x[2],2*y[2],x[2]*x[2]+y[2]*y[2]);
		printf("%.3f %.3f %.3f\n",res.first+x0,res.second+y0,hypot(res.first,res.second));
	}
	
	return 0;
}

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

#define rep(i, n) for(int i = 0; i < n; i ++)
#define COUNT(i, n) for(int i = 1; i <= n; i ++)
#define ITER(c) __typeof((c).begin())
#define each(c, it) for(ITER(c) it =(c).begin(); it!=(c).end(); it++)
#define ALL(c) c.begin(), c.end()
#define mp make_pair
#define pb push_back
#define MEMSET(v, h) memset((v), h, sizeof(v))
 
using namespace std; 

typedef pair<int, int> pii;
typedef long long ll;
typedef vector<int> vi;
typedef vector<string> vs;

const int INF = 1 << 24;

int main(void){
    int n; cin >> n;

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

        double a1 = 2 * (x2 - x1), a2 = 2 * (x3 - x1),
               b1 = 2 * (y2 - y1), b2 = 2 * (y3 - y1),
               c1 = x1 * x1 - x2 * x2 + y1 * y1 - y2 * y2,
               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(pow(x1 - px, 2) + pow(y1 - py, 2));

        printf("%.3f %.3f %.3f\n", px, py, r);
    }
 
    return 0;
}