Go: package main

import (
	"bufio"
	"os"
	"strconv"
	"fmt"
	"strings"
)

var scanner = bufio.NewScanner(os.Stdin)

func nextInt() int {
	scanner.Scan()
	i, e := strconv.Atoi(scanner.Text())
	if e != nil {
		panic(e)
	}
	return i
}

func main() {
	n := nextInt()
	for i := 0; i < n; i++ {
		scanner.Scan()
		points := strings.Split(scanner.Text(), " ")
		fpoints := make([]float64, 0)
		for _, v := range points {
			tmp, _ := strconv.ParseFloat(v, 64)
			fpoints = append(fpoints, tmp)
		}
		if fpoints[0] == fpoints[2] && fpoints[1] == fpoints[3] {
			fmt.Println("YES")
			continue
		}
		a := (fpoints[1]-fpoints[3])/(fpoints[0]-fpoints[2])
		b := (fpoints[5]-fpoints[7])/(fpoints[4]-fpoints[6])
		if a == b {
			fmt.Println("YES")
		} else {
			fmt.Println("NO")
		}
	}
}

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

using namespace std;

int main(void) {
	int ds;
	cin >> ds;
	
	for(int i = 0; i < ds; i++) {
		double X[4], Y[4];
		double a1, a2;
		double b1, b2;
		
		for(int j = 0; j < 4; j++) {
			cin >> X[j] >> Y[j];
		}
		a1 = abs(Y[1] - Y[0]);
		b1 = (X[1] - X[0]);
		
		a2 = abs(Y[3] - Y[2]);
		b2 = (X[3] - X[2]);
		
		a1 /= b1;
		a2 /= b2;
		
		if(a1 == a2) {
			cout << "YES" << endl;
		} else {
			cout << "NO" << endl;
		}
	}
	return 0;
}

C++: // clang-format off
#include <bits/stdc++.h>
#define int long long
#define main signed main()
// #define main int main()
#define loop(i, a, n) for (int i = (a); i < (n); i++)
#define rep(i, n) loop(i, 0, n)
#define all(v) (v).begin(), (v).end()
#define rall(v) (v).rbegin(), (v).rend()
#define prec(n) fixed << setprecision(n)
#define stlice(from, to) substr(from, (to) - (from) + 1)
#define pb push_back
#define mp make_pair
#define mt make_tuple
#define fi first
#define se second
using namespace std;
using pii = pair<int, int>;
using vi = vector<int>;
using vd = vector<double>;
using vc = vector<char>;
using vb = vector<bool>;
using vs = vector<string>;
using vpii = vector<pii>;
using vvi = vector<vi>;
using vvb = vector<vb>;
using vvpii = vector<vpii>;
template<typename A> using fn = function<A>;
constexpr int INF = sizeof(int) == sizeof(long long) ? 1000000000000000000LL : 1000000000;
constexpr int MOD = 1000000007;
constexpr double PI = acos(-1);
template<typename A, typename B> bool cmin(A &a, const B &b) { return a > b ? (a = b, true) : false; }
template<typename A, typename B> bool cmax(A &a, const B &b) { return a < b ? (a = b, true) : false; }
constexpr bool odd(const int &n) { return n & 1; }
constexpr bool even(const int &n) { return !odd(n); }
template<typename V> constexpr typename V::value_type sum(const V &v) { return accumulate(all(v), 0); }
void solve();
main { solve(); return 0; }
// clang-format on

void solve() {
  int n;
  cin >> n;
  rep(i, n) {
    double x1, y1, x2, y2, x3, y3, x4, y4;
    cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3 >> x4 >> y4;
    if (x1 == x2 && x3 == x4) {
      cout << "YES" << endl;
      return;
    }
    if (x1 == x2 || x3 == x4) {
      cout << "NO" << endl;
      return;
    }
    if ((y1 - y2) * (x3 - x4) == (y3 - y4) * (x1 - x2)) {
      cout << "YES" << endl;
    } else {
      cout << "NO" << endl;
    }
  }
}

C++: #include<cmath>
#include<iostream>
#include<algorithm>
#include<iomanip>
#include<vector>
#include<string>
#include<queue>
#include<stack>
#include<cstdio>
#include<map>
#define rep(i,n) for(int i=0;i<n;i++)
#define fori(i,k,n) for(int i=k;i<n;i++)
using namespace std;
const int dx[4] = { 0, 1, 0, -1 }, dy[4] = { 1, 0, -1, 0 };
const int dX[8] = { 0, 1, 1, 1, 0, -1, -1, -1 }, dY[8] = { 1, 1, 0, -1, -1, -1, 0, 1 };
/*
(char)'1' - (int)48 = (int)1; 


*/


int main()
{
	int n;
	cin >> n;
	while (n--){
		double x[4], y[4];
		rep(i, 4)cin >> x[i]>>y[i];
		if (x[0] == x[1])
		{
			if (x[2] == x[3])cout << "YES" << endl;
			else cout << "NO" << endl;
		}
		else if (x[2] == x[3])
		{
			cout << "NO" << endl;
		}
		else if ((x[0] - x[1])*(y[2] - y[3]) == (x[2] - x[3])*(y[0] - y[1]))
			cout << "YES" << endl;
		else cout << "NO" << endl;

	}
	return 0;

}

C++: #include <bits/stdc++.h>
using namespace std;
const eps = 1e-7;

int main() {
    int n;
    double x1, y1, x2, y2, x3, y3, x4, y4;
    cin >> n;
    while(n--) {
        cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3 >> x4 >> y4;
        cout << (abs((x2-x1)*(y4-y3) - (x4-x3)*(y2-y1)) < eps ? "YES" : "NO") << endl;
    }
    return 0;
}

C++: #include <iostream>
using namespace std;
int main() {
    cout << "In preparation." << endl;
    return 0;
}

C++: #include<iostream>
#include<string>
#include<cmath>
#include<queue>
#include<vector>
#include<functional>
using namespace std;
int main() {
	int n;
	double x1, y1, x2, y2, x3, y3, x4, y4;
	cin >> n;
	for (int z = 0; z < n; z++) {
		cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3 >> x4 >> y4;
		double a = 99999, b = 99999;
		if (x2 - x1 != 0) {
			a = (y2 - y1) / (x2 - x1);
		}
		if (x4 - x3 != 0) {
			b = (y4 - y3) / (x4 - x3);
		}
		if (a == b) cout << "YES" << endl;
		else cout << "NO" << endl;
	}
}

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

typedef pair<double, double> pdd;

int main(void) {
  pdd zahyo[4];
  int n;
  cin >> n;

  while (n--) {
    for (int i = 0; i < 4; i++) {
      cin >> zahyo[i].first >> zahyo[i].second;
    }
    
    double angle1, angle2;
    angle1 = (zahyo[1].second - zahyo[0].second) / (zahyo[1].first - zahyo[0].first);
    angle2 = (zahyo[3].second - zahyo[2].second) / (zahyo[3].first - zahyo[2].first);

    if (angle1 == angle2) {
      cout << "YES" << endl;
    } else {
      cout << "NO" << endl;
    }
  }

  return 0;
}

C++: #include <iostream>

using namespace std;

int main()
{
	int n;
	double x[4], y[4];

	cin >> n;

	for(int i = 0; i < n; i++){
		cin >> x[0] >> y[0] >> x[1] >> y[1] >> x[2] >> y[2] >> x[3] >> y[3];

		if(((y[1]-y[0])/(x[1]-x[0])) == ((y[3]-y[2])/(x[3]-x[2])))
			cout << "YES" << endl;
		else 
			cout << "NO" << endl;
	}

	return 0;
}

C++: #include <stdio.h>

int
main(void)
{
	char line[100];
	int n;

	if (fgets(line, sizeof line, stdin) == NULL) {
		return 1;
	}
	if (sscanf(line, "%d", &n) != 1) {
		return 1;
	}

	for (int i = 0; i < n; i++) {
		if (fgets(line, sizeof line, stdin) == NULL) {
			return 1;
		}
		
		double x1, y1, x2, y2, x3, y3, x4, y4;
		
		if (sscanf(line, "%lf %lf %lf %lf %lf %lf %lf %lf",
				   &x1, &y1, &x2, &y2, &x3, &y3, &x4, &y4) != 8) {
			return 1;
		}
		
		double ab = (y2 - y1)/(x2 - x1);
		double cd = (y4 - y3)/(x4 - x3);
		
		printf("%s\n", ((ab == cd) ? "YES" : "NO"));
	}

	return 0;
}

C++: #include<stdio.h>
 
int main(){
    int a;
    scanf("%d",&a);
    for(int i=0;i<a;i++){
        double x1,x2,x3,x4,y1,y2,y3,y4;
        scanf("%lf%lf%lf%lf%lf%lf%lf%lf",&x1,&y1,&x2,&y2,&x3,&y3,&x4,&y4);
        if(x1==x2&&x3==x4)printf("YES\n");
        else{
            if((y1-y2)/(x1-x2)==(y3-y4)/(x3-x4))printf("YES\n");
            else printf("NO\n");
        }
    }
}

C++: #include <iostream>
using namespace std;
int main(){
    int n;
    cin >> n;
    double x1,x2,x3,x4,y1,y2,y3,y4;
    for(int i=0;i<n;i++){
        cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3 >> x4 >> y4;
        if(x4-x3==0 || x2-x1==0){
            if(x4-x3==0 && x2-x1==0)
                cout << "YES" << endl;
            else
                cout << "NO" << endl;
        }
        else{
            double p=(y2-y1)/(x2-x1);
            double q=(y4-y3)/(y2-y1);
            if(p==q)
                cout << "YES" << endl;
            else
                cout << "NO" << endl;
        }
    }

}