Functions and their Properties
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Questions and Answers

What is the name of the set X in the context of functions?

Domain

Given a relation f: X →Y, what condition must hold for f(x) to be a function?

For every x ∈ X, there must exist a unique y ∈ Y such that y = f(x).

The vertical line test is used to determine if a relation is a function graphically.

True (A)

Which of the following relations is a function?

<p>f(x) = 2x + 1 (B)</p> Signup and view all the answers

A function from a set D to a set Y is a ______ that assigns a unique element to each element in D.

<p>rule</p> Signup and view all the answers

The output of a function is also known as its range.

<p>False (B)</p> Signup and view all the answers

What is the horizontal line test used to determine?

<p>Whether a function is one-to-one</p> Signup and view all the answers

Which of the following functions is one-to-one?

<p>y = √x (B)</p> Signup and view all the answers

What is the inverse of a function?

<p>Another function that reverses the mapping of the original function.</p> Signup and view all the answers

A function and its inverse are always symmetrical about the line y = x.

<p>True (A)</p> Signup and view all the answers

What is the first step typically involved in finding the inverse of a function?

<p>Show that the function is one-to-one.</p> Signup and view all the answers

How can you graphically find the inverse of a function?

<p>Reflect the graph of f over the line y = x (B)</p> Signup and view all the answers

Flashcards

Function

A rule that assigns a unique element from a set (Y) to each element of another set (X).

Vertical Line Test

A graphical method to determine if a graph represents a function. A graph is a function if no vertical line intersects the graph more than once.

Domain

The set of all possible input values (x) for a function.

Range

The set of all possible output values (y) for a function.

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One-to-One Function

A function where each input value results in a unique output value; and distinct input values have distinct output values.

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Horizontal Line Test

A graphical method to determine if a function is one-to-one. A function is one-to-one if no horizontal line intersects the graph more than once.

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Inverse Function

A function that reverses the action of another function, undoing the operation.

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f⁻¹(x)

Notation for the inverse function of f(x).

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f(x)=2x+1

A linear function with a slope of 2 and a y-intercept of 1.

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y=x²

A quadratic function that produces a parabola.

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y=x³

A cubic function that produces an S-shaped curve.

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Finding the inverse of a function

Finding the function that reverses the operation of the original function.

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f(x) = √x

A square root function with a domain of x ≥ 0 and range of y ≥ 0.

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f(x) = 1/x

A reciprocal function with domain excluding zero and range excluding zero.

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Graph Symmetry

A visual relationship between two graphs.

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Algebraic method for inverse

Finding the inverse by solving for x in terms of y, swapping variables and simplifying.

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Graph method for inverse

Finding the inverse by reflecting the function graph over y=x line.

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g(f(x)) = x

A verification step that g(x) is the inverse of f(x).

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f(x) is one-to-one

Each input has a unique output and no two inputs share the same output.

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Domain of f⁻¹(x)

Same as the range of f(x).

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Study Notes

Functions

  • A function maps elements from a set (domain) to a set (co-domain)
  • A function assigns a unique output value for each input value
  • Algebraically: for all x in the domain, there's a unique y in the co-domain such that y = f(x)
  • Graphically: the vertical line test - a relation is a function if any vertical line intersects the graph at most once.

Example Functions

  • f(x) = 2x + 1 is a function
  • x² + y² = 9 is not a function

Domain and Range

  • Domain: the set of all possible input values (x-values)
  • Range: the set of all possible output values (y-values)

Examples of function Types and Domains

  • y = x² Domain: (-∞, ∞) Range: [0, ∞)
  • y = 1/x Domain: (-∞, 0) U (0, ∞) Range: (-∞, 0) U (0, ∞)
  • y = √x Domain: [0, ∞) Range: [0, ∞)
  • y = √(4 - x) Domain: (-∞, 4] Range: [0, ∞)
  • y = √(1 - x²) Domain: [-1, 1] Range: [0, 1]

One-to-One Functions

  • A function f(x) is one-to-one if f(x₁) ≠ f(x₂) whenever x₁ ≠ x₂
  • Algebraically: f(x₁) = f(x₂) implies x₁ = x₂
  • Graphically: the horizontal line test - a function is one-to-one if any horizontal line intersects the graph at most once.

Inverse Functions

  • An inverse function reverses the relationship of a one-to-one function
  • g(x) is the inverse of f(x) if g(f(x)) = x for all x in the domain of f(x) and f(g(x))=x for all x in the domain of g(x).
  • Notation: g(x) is often written as f⁻¹(x).
  • f⁻¹(f(x)) = x and f(f⁻¹(y)) = y
  • To find the inverse, solve for x in terms of y, then swap x and y.
  • Example: If y = (1/2)x + 1, f⁻¹(x) = 2x - 2

How to Sketch the Inverse

  • Draw the line y = x
  • Reflect the graph of f over the line y = x. The reflection is f⁻¹(x)

Finding an Inverse Function

  • Given a function, replace y with f(x). Solve for x in terms of y. Swap x and y. Replace y with f⁻¹(x).
  • Example: if y=√x then x = y^2 and f^(-1) (x)=x^2.

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Related Documents

Math 1 (MA111) Lecture 2 PDF

Description

Explore the concepts of functions, including their definitions, domains, and ranges. This quiz will cover various types of functions and the vertical line test to determine function validity. Test your knowledge on one-to-one functions and example functions provided.

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