/*    Rohan Balot
    NSIT, New Delhi  */
#include <bits/stdc++.h>
using namespace std;
                             
#define ALL(t) (t).begin(), (t).end()
#define mp make_pair
#define show(t) copy((t).begin(), (t).end(), ostream_iterator<int>(cout, ' '))
const int N = 77778; 
const int M = 77778; 

void __answer() 
{
	int n;
	cin >> n;
	set <int> s;
	for (int i = 0; i < n; i++) {
		int x, y;
		cin >> x >> y;
		s.insert(abs(x));
		s.insert(abs(y));
	}
	if(s.size() == 2) 
		cout << "YES\n";
	else 
		cout << "NO\n";
}
int main()
{
    ios::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
    #ifdef LOCAL
        freopen("sample_input.txt","r",stdin);
    #endif
    size_t _t;
    cin >> _t;
    cin.ignore();
    while (_t--) {
        __answer();
    }
    return 0;
}