Graphing Reciprocal Functions
Concept

Reciprocal Function

The reciprocal function is a function that pairs each x-value with its reciprocal.
Table of values of the function y=1/x
The function rule of this reciprocal function is obtained algebraically by writing the rule for the pairings shown in the table.


f(x) = 1/x, x≠0

The graph of the function f(x) = 1x is a hyperbola, which consists of two symmetrical parts called branches. It has two asymptotes, the x- and y-axes. The domain and range are all nonzero real numbers.

Graph of y = 1/x with horizontal asymptote at y = 0 and vertical asymptote at x = 0. Points (-2, -1/2), (-1, -1), (-0.5, -2), (2, 1/2), (1, 1), and (0.5, 2) are plotted on the graph.

The graph of y= 1x can be used to graph other reciprocal functions. This can be done by applying different transformations.

Name Equation Characteristics
Parent Reciprocal Function y=1/x Domain: & R-{0} Range: & R-{0} Asymptotes: & x- andy-axes
Inverse Variation Functions y=a/x
General Form of Reciprocal Functions y=a/x-h+k Domain: & R-{h} Range: & R-{k} Asymptotes: & x = h andy=k

The general form of reciprocal functions is also known as the simple rational function.

Extra

Reciprocal vs. Inverse of a Function

It is important not to confuse the reciprocal of a function with the inverse of a function. For numbers, a^(-1) refers to the reciprocal 1a, while the notation f^(- 1)(x) is commonly used to refer to the inverse of a function.

Function, f Reciprocal, 1f Inverse, f^(-1)
f(x) = 2x + 10 1/f(x)=1/2x+10 f^(- 1)(x) = 1/2(x - 10 )
f(x) = x^3 - 5 1/f(x)=1/x^3-5 f^(- 1)(x) = sqrt(x + 5)
Exercises