Is the set {0}, an empty set?

Which of the following is an empty set?

Is the region represented by 2x+3yle18,x+yge10,xge0, yge0 an empty set?

If the equation x^2-y^2-2x-2y+c=0 represent an empty set , then find the value of c.

The set phi is

Fill in the blank: The identity relation on any non-empty set is always an ______ relation.

Let A and B be two non empty sets, then show that AxxB=BxxA . If A=B

State whether the following statement is true or false. If the statement is false, rewrite the given statement correctly. If A and B are non-empty sets, then A xx B is a non-empty set of ordered pairs (x, y) such that x in A and y in B .