Understanding Functions and Their Notation

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Questions and Answers

Given the functions $f(x) = x^2 + 1$ and $g(x) = 2x - 3$, what is the result of $(g \circ f)(2)$?

  • 12
  • 9
  • 3
  • 7 (correct)

Which of the following function types is characterized by having a potential vertical asymptote?

  • Rational functions (correct)
  • Exponential functions
  • Polynomial functions
  • Trigonometric functions

If $f(x) = x^3$ and $g(x) = \sqrt{x}$, which of the following operations results in a function that is not defined for all real numbers?

  • $(g / f)(x)$ (correct)
  • $(f - g)(x)$
  • $(f * g)(x)$
  • $(f + g)(x)$

Which of the following relations is NOT a function, according to the vertical line test?

<p>A circle centered at the origin (C)</p> Signup and view all the answers

If $h(x)$ is a piecewise function where $h(x) = x + 1$ for $x < 0$, and $h(x) = x^2$ for $x \ge 0$, what is the value of $h(-1) + h(2)$?

<p>5 (B)</p> Signup and view all the answers

Which statement accurately describes the relationship between a function's range and its codomain?

<p>The range is always a subset of the codomain. (C)</p> Signup and view all the answers

A function is considered bijective if it is:

<p>Both one-to-one and onto. (A)</p> Signup and view all the answers

Given a function f: A → B, what condition must be met for f to be a valid function?

<p>Every element in A must be associated with exactly one element in B. (D)</p> Signup and view all the answers

What is the defining characteristic of a constant function?

<p>Its output value is always the same regardless of the input value. (B)</p> Signup and view all the answers

If a function f is bijective, what can be inferred about its inverse function f⁻¹?

<p>The domain of f⁻¹ is the range of f and the range of f⁻¹ is the domain of f. (A)</p> Signup and view all the answers

Consider two functions f and g. What is involved in 'composition of functions'?

<p>Applying one function to the result of another, i.e. g(f(x)). (B)</p> Signup and view all the answers

Which of the following equations represents a linear function?

<p>$f(x) = 5x - 7$ (D)</p> Signup and view all the answers

If a function has a range that is a subset of its codomain, and not all elements of its codomain are in the range, the given function is:

<p>Neither onto nor bijective. (D)</p> Signup and view all the answers

Flashcards

Polynomial function

A function that can be expressed as a sum of terms, each of which is a constant multiplied by a non-negative integer power of the variable.

Rational function

A function formed by dividing two polynomial functions.

Exponential function

A function where the input variable appears as an exponent.

Logarithmic function

A function that reverses the process of an exponential function.

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Vertical line test

A method to determine if a relation is a function by checking if any vertical line intersects the graph more than once. If it does, the relation is not a function.

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What is a function?

A relation between a set of inputs (domain) and a set of possible outputs (codomain) where each input has exactly one output.

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What is the domain?

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

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What is the codomain?

The set of all possible output values (y-values) that a function could potentially map to.

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What is range?

The set of all possible output values (y-values) corresponding to the inputs in the domain.

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What is a one-to-one function?

A function where each element in the codomain is associated with at most one element in the domain. For example, if f(x₁) = f(x₂), then x₁ = x₂.

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What is an onto function?

A function where every element in the codomain is associated with at least one element in the domain.

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What is a bijective function?

A function that is both one-to-one and onto.

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What is a constant function?

A function that assigns the same output value to every input value.

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Study Notes

Definition of a Function

  • A function is a relation where each input (domain) is associated with exactly one output (codomain).
  • A function from set A to set B maps every element 'a' in A to exactly one element 'b' in B.
  • Functions are often written as f: A → B, where 'f' is the function name, 'A' is the domain, and 'B' is the codomain.

Function Notation

  • f(x) = y represents the output 'y' for input 'x' of function 'f'.
  • 'x' is the input or argument of the function.
  • 'y' is the output or value of the function for input 'x'.
  • An alternative notation is f(x) for the function value.

Types of Functions

  • One-to-one (Injective): If f(x₁) = f(x₂), then x₁ = x₂. Each output is associated with at most one input.
  • Onto (Surjective): Every element in the codomain is associated with at least one element in the domain. The function's range equals the codomain.
  • Bijective: A function that is both one-to-one and onto. Every domain element maps to a unique codomain element, and every codomain element is mapped to by at least one domain element.
  • Constant Functions: Produce the same output for all inputs.
  • Linear Functions: Constant rate of change, graphed as a straight line. Form: f(x) = mx + b, where m is the slope and b is the y-intercept.

Properties of Functions

  • Domain: The set of all possible input values (x-values).
  • Range: The set of all possible output values (y-values) corresponding to inputs in the domain.
  • Codomain: The set of all possible output values a function could map to. The range is a subset of the codomain.
  • Inverse Functions: If 'f' is bijective, an inverse function (f⁻¹) exists, reversing the mapping. The domain of f⁻¹ is the range of f, and the range of f⁻¹ is the domain of f.
  • Composition of Functions: Combining multiple functions, where the output of one is the input of the next. If f: A → B and g: B → C, (g o f)(x) = g(f(x)).

Special Types of Functions (Examples)

  • Polynomial Functions: Functions written as polynomials, e.g., f(x) = x² + 2x + 1.
  • Rational Functions: Functions that are quotients of polynomials, e.g., f(x) = (x+1)/(x-2).
  • Exponential Functions: f(x) = ax, where 'a' is a constant.
  • Logarithmic Functions: Inverses of exponential functions, e.g., f(x) = loga(x).
  • Trigonometric Functions: Relate angles and sides of a right triangle (sin, cos, tan).
  • Piecewise Functions: Defined by different expressions in different intervals of the domain.

Basic Function Operations

  • Function Addition: (f + g)(x) = f(x) + g(x)
  • Function Subtraction: (f - g)(x) = f(x) - g(x)
  • Function Multiplication: (f * g)(x) = f(x) * g(x)
  • Function Division: (f / g)(x) = f(x) / g(x), provided g(x) ≠ 0

Graphing Functions

  • A visual representation of the function's input-output relationship.
  • Plot points (x, f(x)) on a coordinate system.
  • Graph features (intercepts, symmetry, maxima/minima, asymptotes) reflect function properties.

Determining if a Relation is a Function

  • Vertical Line Test: If a vertical line intersects the graph more than once, the relation is not a function.

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