If and are two relations on to , then they are called equal if they are equal as subsets of .
When applied to functions, this means are equal if i.e., , for each .
& codomain of codomain of .
Some operations in functions:
(I) The addition of two functions,i.e., defined by
(ii) The multiplication is defined by
(iii) The quotient is defined by
(iv) The subtraction of the two functions,
is not defined .