Saya mau tau Restrictions and extensions dari Fungsi (matematika). Jelaskan dalam bahasa sunda

Suppose that  is a subset of  and that

The restriction of  to  is then the function . Intuitively, this is the same function as  except that we restrict the domain of  to .

An extension of a function  is a function  defined on a superset  of  such that . Provided the domain of  is not the universal set,  always has lots of extensions.