Determine whether the given subset U ofR2 is a subspace. Indicate (shade) the subset U in the plane. In case of failure, list the condition(s) that...

I do not understand how these subspaces work without giving actual values. Please help

Determine whether the given subset U ofR2 is a subspace. Indicate (shade) the subset U in the plane. In case offailure, list the condition(s) that are false.13. { (x, y) | xy 2 0}14. { ( x, y ) | x = y}15. { (x, y ) | x2 = yz}16. { ( x, y ) | x = yz }