Personal collections
Functions can be added, subtracted, multiplied and divided. Let's review the operations.
The sum or difference of two functions 
and 
defined on an interval 
is a function 
defined on the same interval and for each 
in the domain:
The product of two functions and defined on an interval is a function 
defined on the same interval and for each in the domain:
The quotient of the two functions and defined on some interval is the function 
defined on the same interval , except for those for which 
. For each in the domain:
; 
