# Enter your code here. Read input from STDIN. Print output to STDOUT
from collections import Counter
q=int(raw_input())

def rect(n):
    res=[]
    for i in xrange(len(n)-1):
         res.append((n[i][0] - n[i+1][0])//(n[i][1] - n[i+1][1]))
    if dict(Counter(res)).get(-1,0) >= 2:
        return 'NO'
    else:
        return 'YES'

for i in xrange(q):
    n=int(raw_input())
    points=[]
    for i in xrange(n):
        points.append(map(int,raw_input().split(' ')))
    print rect(sorted(points,key=lambda x:(x[0],x[1])))