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))
	}
}

Python: def perpendicular_bisector(p, q):
    x = (q[0] - p[0])
    y = (q[1] - p[1])
    return (2 * x, 2 * y, -x**2 - y**2)


def gauss_jordan_elimination(Array):
    # N???M??????Array
    N = len(Array)
    if N == 0:
        return (True, Array)
    else:
        M = len(Array[0])

    A = []
    for i in range(len(Array)):
        A.append(Array[i][:])

    pivot = 0
    L = min(N, M)
    while pivot < L:
        pivot_v = A[pivot][pivot]
        pivot_row = pivot
        for i in range(pivot + 1, L):
            v = max(A[i][pivot], -A[i][pivot])
            if pivot_v < v:
                pivot_row = i
                pivot_v = v
        if pivot_row > pivot:
            for i in range(M):
                A[pivot][i], A[pivot_row][i] = A[pivot_row][i], A[pivot][i]
        if pivot_v == 0:
            return ('False', A)
        inv_pivot = 1 / A[pivot][pivot]
        A[pivot][pivot] = 1
        for i in range(pivot + 1, M):
            A[pivot][i] *= inv_pivot
        for i in range(N):
            if i == pivot:
                continue
            t = -1 * A[i][pivot]
            A[i][pivot] = 0
            for j in range(pivot + 1, M):
                A[i][j] += t * A[pivot][j]
        pivot += 1
    return ('True', A)

n = int(input())
for _ in range(n):
    x1, y1, x2, y2, x3, y3 = map(float, input().split())


    a = list(perpendicular_bisector((x1, y1), (x2, y2)))
    b = list(perpendicular_bisector((x1, y1), (x3, y3)))
    c = [a, b]
    state, c = gauss_jordan_elimination(c)
    x = c[0][2]
    y = c[1][2]
    r = ((x - x1)**2 + (y - y1)**2)**0.5
    print(round(x, 3), round(y, 3), round(r, 3))

Python: import math
from decimal import Decimal, ROUND_HALF_EVEN, ROUND_HALF_UP

n = int(input())

for _ in range(n):
    x1, y1, x2, y2, x3, y3 = map(float, input().split())

    a2 = (x2-x3)**2 + (y2-y3)**2
    b2 = (x1-x3)**2 + (y1-y3)**2
    c2 = (x1-x2)**2 + (y1-y2)**2
    area = ((x2-x1) * (y3-y1) - (x3-x1) * (y2-y1)) / 2

    x = (a2*(b2+c2-a2)*x1 + b2*(c2+a2-b2) *
         x2 + c2*(a2+b2-c2)*x3) / (16*area*area)
    y = (a2*(b2+c2-a2)*y1 + b2*(c2+a2-b2) *
         y2 + c2*(a2+b2-c2)*y3) / (16*area*area)
    r = ((x1-x)**2 + (y1-y)**2)**0.5

    x = Decimal(str(x)).quantize(Decimal("0.001"), rounding=ROUND_HALF_UP)
    y = Decimal(str(y)).quantize(Decimal("0.001"), rounding=ROUND_HALF_UP)
    r = Decimal(str(r)).quantize(Decimal("0.001"), rounding=ROUND_HALF_UP)

    print(x, y, r)

Python: from math import sqrt, fabs


def calcu_cirucumcenter(x1, y1, x2, y2, x3, y3):
    """
   ??????O?????§?¨????(x, y)??¨????????¨
   (x-x1)**2 + (y-y1)**2 = (x-x2)**2 + (y-y2)**2
   x**2 -2*x1*x + x1**2 + y**2 -2*y1*y + y1**2 = ... -2*x2*x, x2**2, -2*y2*y, y2**2
   ?????¨????????¨ (-2*x1 + 2*x2)x + (-2y1 + 2*y2)y + (x1**2 + y1**2 - x2**2 - y2**2) = 0
   x1, x3???????????????????§????
   (-2*x1 + 2*x3)x + (-2y1 + 2*y3)y + (x1**2 + y1**2 - x3**2 - y3**2) = 0
   
   ??????????????¢????????\????????¢???????????£???????¨??????¨???????§£???
   | a b | = |e|
   | c d |   |f|
   """
    a = -2 * x1 + 2 * x2
    b = -2 * y1 + 2 * y2
    c = -2 * x1 + 2 * x3
    d = -2 * y1 + 2 * y3
    e = -1* (x1 ** 2 + y1 ** 2 - x2 ** 2 - y2 ** 2)
    f = -1 * (x1 ** 2 + y1 ** 2 - x3 ** 2 - y3 ** 2)

    x = 1 / (a * d - b * c) * (d * e - b * f)
    y = 1 / (a * d - b * c) * (-c * e + a * f)
    return x, y


if __name__ == '__main__':
    epsilon = 1e-9

    # ??????????????\???
    num = int(input())
    for i in range(num):
        x1, y1, x2, y2, x3, y3 = [float(x) for x in input().split(' ')]

        # ?????\????????????(??????)????±???????
        x, y = calcu_cirucumcenter(x1, y1, x2, y2, x3, y3)
        # ?¨????????????¨?????? -0.0 ???????????´???????????¶?????? 0.0 ?????????
        if fabs(x) < epsilon:
            x = 0.0
        if fabs(y) < epsilon:
            y = 0.0

        # ????????????????????§????????¢?????????
        r = sqrt((x - x1)**2 + (y - y1)**2)

        print('{0:.3f} {1:.3f} {2:.3f}'.format(x, y, r))