Skip to main content
Ch. 2 - Functions and Graphs
Blitzer - College Algebra 8th Edition
Blitzer8th EditionCollege AlgebraISBN: 9780136970514Not the one you use?Change textbook
Chapter 3, Problem 24

In Exercises 11–26, determine whether each equation defines y as a function of x. xy - 5y =1

Verified step by step guidance
1
Start with the given equation: \(xy - 5y = 1\).
Factor out \(y\) from the left side: \(y(x - 5) = 1\).
Solve for \(y\) by dividing both sides by \((x - 5)\), assuming \(x \neq 5\): \(y = \frac{1}{x - 5}\).
Analyze the expression for \(y\): for each value of \(x\) (except \(x = 5\)), there is exactly one corresponding value of \(y\).
Conclude that since \(y\) can be written as a single-valued function of \(x\) (except at \(x = 5\) where it is undefined), the equation defines \(y\) as a function of \(x\) on its domain.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above.
Video duration:
2m
Was this helpful?

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Definition of a Function

A function is a relation where each input (x-value) corresponds to exactly one output (y-value). To determine if an equation defines y as a function of x, we check if for every x there is only one y that satisfies the equation.
Recommended video:
5:57
Graphs of Common Functions

Implicit vs. Explicit Functions

An explicit function expresses y directly in terms of x (e.g., y = f(x)), while an implicit function involves both variables in an equation (e.g., xy - 5y = 1). Understanding how to manipulate implicit equations helps determine if y can be uniquely solved for each x.
Recommended video:
3:18
Permutations vs. Combinations

Solving for y and the Vertical Line Test

To check if y is a function of x, solve the equation for y. If you get one unique y for each x, it is a function. Graphically, the vertical line test states that if any vertical line crosses the graph more than once, y is not a function of x.
Recommended video:
Guided course
05:17
Types of Slope