test = int(input())
for testcase in range(test):
    n = int(input())
    quer = []
    for query in range(n):
        quer.append(list(map(int,input().strip().split(' '))))
    temp = sorted(quer,key=lambda x:x[0],reverse=True)
    for x in temp:
        if(x[1]==0):
            largestX = x[0]
            break
    temp = sorted(quer,key=lambda x:x[1],reverse=True)
    for x in temp:
        if(x[0]==0):
            largestY = x[1]
            break
    ans = 'YES'
    for x in quer:
        if(x[0]==0 or x==largestX):
            if(x[1]>largestY or x[1]<0):
                ans = 'NO'
                break
        elif(x[1]==0 or x[0]==largestX):
            if(x[0]>largestX or x[1]<0):
                ans = 'NO'
                break
        else:
            ans = 'NO'
            break
    print(ans)