n=int(input())
for j in range(n):
    s=int(input())
    x=[]
    y=[]
    for i in range(s):
        a,b=map(int,input().split())
        x.append(abs(a))
        y.append(abs(b))
    p=max(x)
    q=max(y)
    ws=10
    for i in range(0,s):
        if(x[i]==0 or y[i]==0):
            continue
        elif((x[i]==p and y[i]<=q)) :
            continue
        elif(x[i]<=p and y[i]==q):
            continue
        else:
            ws=0
            break
    if(ws==0):
        print("NO")
    else:
        print("YES")