Concept:
If two functions f and g have numbers as output, they may be combined with the operations of arithmetic to form the sum function f + g, the difference function f - g, the product function f⋅g, and the quotient function 
. These functions are defined as follows:
the sum function (f + g)(x) = f(x) + g(x)
the difference function (f - g)(x) = f(x) - g(x)
the product function (f ⋅ g)(x) = f(x) ⋅ g(x)
the quotient function
the difference function (f - g)(x) = f(x) - g(x)
the product function (f ⋅ g)(x) = f(x) ⋅ g(x)
the quotient function
A direct consequence of these definitions is that the y-values for the graph of a combination function can be found by adding, subtracting, multiplying, or dividing the y-values of the individual functions.
