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: def main():
    import math
    for i in range(int(input())):
        x1,y1,x2,y2,x3,y3=map(float,input().split())

        a=y1-y2
        b=y1-y3

        if a==0:
            x=(x1+x2)/2
            c=(x3-x1)/(y1-y3)
            d=c*(-x1-x3)/2+(y1+y3)/2
            y=c*x+d

        elif b==0:
            x=(x1+x3)/2
            c=(x2-x1)/(y1-y2)
            d=c*(-x1-x2)/2+(y1+y2)/2
            y=c*x+d

        else:
            a=(x2-x1)/(y1-y2)
            b=a*(-x1-x2)/2+(y1+y2)/2
            c=(x3-x1)/(y1-y3)
            d=c*(-x1-x3)/2+(y1+y3)/2

            x=(d-b)/(a-c)
            y=a*x+b

        r=math.sqrt((x-x1)**2+(y-y1)**2)

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

Python: import math
n = int(input())
for i in range(n):
    x1,y1,x2,y2,x3,y3 = map(float,input().split())
    a = 2*(x2 - x1)
    b = 2*(y2 - y1)
    c = x2**2 + y2**2 - x1**2 -y1**2
    d = 2*(x3 - x1)
    e = 2*(y3 - y1)
    f = x3**2 + y3**2 - x1**2 -y1**2
    x = (c*e - f*b)/(a*e - b*d)
    y = (c*d - f*a)/(b*d - e*a)
    r = math.sqrt((x1 - x)**2 + (y1 - y)**2)
    x = round(x,3)
    y = round(y,3)
    r = round(r,3)
    if x == -0.0:
        x = 0.0
    if y == -0.0:
        y = 0.0
    print("{0:.3f}".format(x),end = ' ')
    print("{0:.3f}".format(y),end = ' ')
    print("{0:.3f}".format(r))

Python: 
import sys
import math


def solv(x1, y1, x2, y2, x3, y3):
    if y2 == y1:
        xp = 0.5 * (x1 + x2)
        yp = (x3 - x1)/(y3 - y1) * xp + 0.5 * (y1 + y3 - (x3**2 - x1**2)/(y3 - y1))
    elif y3 == y1:
        xp = 0.5 * (x1 + x3)
        yp = (x2 - x1)/(y2 - y1) * xp + 0.5 * (y1 + y2 - (x2**2 - x1**2)/(y2 - y1))
    else:
        xp = 0.5 * (y3 - y2 - (x3**2 - x1**2)/(y3 - y1) + (x2**2 - x1**2)/(y2 - y1))/((x2 - x1)/(y2 - y1) - (x3 - x1)/(y3 - y1))
        yp = (x2 - x1)/(y2 - y1) * xp + 0.5 * (y1 + y2 - (x2**2 - x1**2)/(y2 - y1))
    r = math.sqrt((x1 - xp)**2 + (y1 - yp)**2)
    return (xp, yp, r)



#input_file = open(sys.argv[1], "r")
#lines = input_file.readlines()
lines = sys.stdin.readlines()
lines.pop(0)

for line in lines:
    l = map((lambda x: float(x)), line.split(' '))
    x1 = l[0]
    y1 = l[1]
    x2 = l[2]
    y2 = l[3]
    x3 = l[4]
    y3 = l[5]
    xp, yp, r = solv(x1, y1, x2, y2, x3, y3)
    print("%5.3f %5.3f %5.3f" % (round(xp, 3), round(yp, 3), round(r, 3)))