I need explanation : SET THEORY

Q.1 This is Cantor's groundbreaking work that provides the mathematical basis for making sense of statements like "infinity plus ten is infinity," or "infinity plus infinite is infinity." Here we understand "infinity" to mean "aleph null," which is used in set theory to denote the cardinality of the set of natural numbers {1, 2, 3, ...}.

6) Explain why the quantity "infinity - infinity" is not defined.

Question

I need explanation : SET THEORY 

Q.1 This is Cantor's groundbreaking work that provides the mathematical basis for making sense of statements like "infinity plus ten is infinity," or "infinity plus infinite is infinity." Here we understand "infinity" to mean "aleph null," which is used in set theory to denote the cardinality of the set of natural numbers {1, 2, 3, ...}. 

6) Explain why the quantity "infinity - infinity" is not defined.

lgbasallote · Answer

you have to prove $\infty - \infty$ is indeterminate using set theory?

anonymous · Answer

yes