Go: package main

import "fmt"

func abs(x float64) float64 {
	if x < 0 {
		return -x
	}
	return x
}

func main() {
	var n int
	var x1, y1, x2, y2, x3, y3, x4, y4 float64
	fmt.Scan(&n)
	for i := 0 ; i < n; i++ {
		fmt.Scanf("%f %f %f %f %f %f %f %f", &x1, &y1, &x2, &y2, &x3, &y3, &x4, &y4)
		if abs((x2-x1)*(y4-y3) - (y2-y1)*(x4-x3)) < 1e-10 {
			fmt.Println("YES")
		} else {
			fmt.Println("NO")
		}
	}
}

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) {
      if (x3 == x4) {
        cout << "YES" << endl;
      } else {
        cout << "NO" << endl;
      }
      continue;
    }
    if ((y1 - y2) / (x1 - x2) == (y3 - y4) / (x3 - x4)) {
      cout << "YES" << endl;
    } else {
      cout << "NO" << endl;
    }
  }
}

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

typedef complex<double> P;

// 許容する誤差ε
#define EPS (1e-10)
// 2つのスカラーが等しいかどうか
#define EQ(a,b) (abs((a)-(b)) < EPS)

// 外積 (cross product) : a×b = |a||b|sinΘ
double cross(P a, P b) {
  return (a.real() * b.imag() - a.imag() * b.real());
}

// 2直線の平行判定 : a//b <=> cross(a, b) = 0
int is_parallel(P a1, P a2, P b1, P b2) {
  return EQ( cross(a1-a2, b1-b2), 0.0 );
}

int main(){
	int n;
	double x1,x2,x3,x4,y1,y2,y3,y4;

	cin >> n;
	for(int i=0 ; i<n ; i++){
		cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3 >> x4 >> y4;
		P a(x1,y1), b(x2,y2), c(x3,y3), d(x4,y4);
		if( is_parallel(a,b,c,d) ){
			cout << "YES" << endl;
		}else{
			cout << "NO" << endl;
		}
	}
}

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

int main(){
	double n, i;
	double x1, y1, x2, y2, x3, y3, x4, y4;
	cin >> n;
	for (i = 0; i < n; i++) {
		cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3 >> x4 >> y4;
		if((y1-y2)*(x3-x4) == (y3-y4)*(x1-x2)){
			cout << "YES" << endl;
		}else{
			cout << "NO" << endl;
		}
	}
	return 0;
}

C++: #define _USE_MATH_DEFINES
#include <iostream>
#include <string>
#include <utility>
#include <algorithm>
#include <queue>
#include <map>
#include <fstream>
#include <array>
#include <utility>
#include <functional>
#include <stack>
#include <math.h>

using namespace std;
typedef long long Int;
#define REP(i , x) for(Int i = 0 ; i < x ; ++i)
typedef pair<int, int> P;


int main()
{
	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;

		double dx1 = x2 - x1;
		double dx2 = x4 - x3;
		double dy1 = y2 - y1;
		double dy2 = y4 - y3;

		string ans = (dy1 / dx1 == dy2 / dx2) ? "YES" : "NO";

		if (!dx1 || !dx2){
			ans = "NO";
		}

		cout << ans << endl;
	}
	return 0;
}

C++: #include <cstdio>
#include <queue>
#include <algorithm>
#include <cmath>

#define rep(i, n) for(int i = 0; i < (n); ++i)

using namespace std;

int n;
double x[4];
double y[4];

int main(){
	scanf("%d", &n);
	rep(i, n){
		rep(j, 4){
			scanf("%lf%lf", x + j, y + j);
		}

		double dx[2];
		double dy[2];
		dx[0] = x[0] - x[1];
		dx[1] = x[2] - x[3];
		dy[0] = y[0] - y[1];
		dy[1] = y[2] - y[3];

		// printf("(%lf, %lf) (%lf, %lf)\n", dx[0], dy[0], dx[1], dy[1]);

		printf("%s\n", dx[0] * dy[1] == dx[1] * dy[0] ? "YES" : "NO");
	}
	return 0;
}

C++: #include<bits/stdc++.h>
using namespace std;

int main(){
    int n;
    double x1,x2,x3,x4,y1,y2,y3,y4;
    cin>>n;
    for(int i=0;i<n;i++){
        cin>>x1>>y1>>x2>>y2>>x3>>y3>>x4>>y4;
 
 
        double a,b;
        a=(y2-y1)/(x2-x1);
        b=(y4-y3)/(x4-x3);
        (a==b)? cout<<"YES"<<endl : cout<<"NO"<<endl;
    }
    return 0;
}

C++: #include <iostream>

using namespace std;

int main(){
	double x1, y1, x2, y2, x3, y3, x4, y4;
	int n; cin >> n;
	for(int i = 0; i < n; i++){
		cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3 >> x4 >> y4;
		if((x1 == x2) && (y1 == y2)){
			cout << "YES" << endl;
		}else if((y2 - y1) / (x2 - x1) == (y4 - y3) / (x4 - x3)){
			cout << "YES" << endl;
		}else{
			cout << "NO" << endl;
		}
	}
	return 0;
}

C++: #include <stdio.h>

int main(void)
{
  int n,i;
  double x1,y1,x2,y2,x3,y3,x4,y4;
  int ans[100];
  
  scanf("%d", &n);
  for(i = 0;i < n;i++){
    scanf("%lf %lf %lf %lf %lf %lf %lf %lf", &x1, &y1, &x2, &y2, &x3, &y3, &x4, &y4);
  
    x2 -= x1;
    y2 -= y1;
    x4 -= x3;
    y4 -= y3;

    if(x2 == 0 || x4 == 0){
      if(x2 == 0 && x4 == 0){
	ans[i] = 1;
      }else{
	ans[i] = 0;
      }
    }else{
      if(y2/x2 == y4/x4){
	ans[i] = 1;
      }else{
	ans[i] = 0;
      }
    }
  }
  for(i = 0;i < n;i++){
    if(ans[i] == 1){
      printf("YES\n");
    }else{
      printf("NO\n");
    }
  }   
  return 0;
}

C++: #include <vector>
#include <list>
#include <map>
#include <set>
#include <deque>
#include <stack>
#include <bitset>
#include <algorithm>
#include <functional>
#include <numeric>
#include <utility>
#include <sstream>
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <ctime>
#include <cstring>

#define ll long long
#define ull unsigned long long
#define pii pair<int,int>
#define vi vector<int>
#define VS vector<string>
#define all(x) x.begin(),x.end()
#define mp make_pair
#define pb push_back

using namespace std;

int main(){
    int n;
    cin >> n;
    for(int i=0; i < n; i++){
        double x1, y1, x2, y2, x3, y3, x4, y4;
        cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3 >> x4 >> y4;
        x1 -= x2; y1 -= y2;
        x3 -= x4; y3 -= y4;
        if(x1/y1 == x3/y3) cout << "YES" << endl;
        else cout << "NO" << endl;
    }
}

C++: #include <iostream>
#include <sstream>
#include <iomanip>
#include <algorithm>
#include <cmath>
#include <string>
#include <vector>
#include <list>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <bitset>
#include <numeric>
#include <climits>
#include <cfloat>
using namespace std;

int main()
{
    int n;
    cin >> n;
    while(n-- > 0){
        vector<double> x(4), y(4);
        for(int i=0; i<4; ++i)
            cin >> x[i] >> y[i];
        if(fabs((y[1]-y[0]) * (x[3]-x[2]) - (y[3]-y[2]) * (x[1]-x[0])) < 1.0e-5)
            cout << "YES" << endl;
        else
            cout << "NO" << endl;
    }
    return 0;
}