Calculus: Limits and Limit Theorems

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Questions and Answers

What is the study of limits necessary for?

  • Calculating the slope of a tangent line
  • Simplifying algebraic expressions
  • Studying change in great detail (correct)
  • Approximating the area under a curve

The variable in a limit can equal the constant it approaches.

False (B)

In mathematical notation, how is 'the limit of f(x) as x approaches c is L' typically written?

lim xc f(x) = L

Limits are the backbone of calculus, and calculus is called the ______ of Change.

<p>Mathematics</p>
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In evaluating $\lim_{x \to 2} (1 + 3x)$ using a table of values, what happens to the value of $f(x)$ as $x$ gets closer to 2?

<p>It approaches 7. (C)</p>
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When evaluating a limit using a table of values, it is sufficient to approach the constant from one direction only.

<p>False (B)</p>
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If the limit of a function as $x$ approaches $c$ from the left is not equal to the limit as $x$ approaches $c$ from the right, what can be concluded about the limit?

<p>The limit does not exist</p>
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Limits that only consider values on one side of $c$ are referred to as ______ limits.

<p>one-sided</p>
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According to the examples, what is the limit of $|x|$ as $x$ approaches 0?

<p>0 (A)</p>
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The limit of a function as $x$ approaches a value can always be determined by simply substituting the value into the function.

<p>False (B)</p>
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When is a limit said to 'not exist'?

<p>When the left-hand limit and the right-hand limit are not equal.</p>
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When evaluating $\lim_{x \to 4} f(x)$ where $f(x)$ approaches 5 from the left and 3 from the right, we say the limit ______.

<p>DNE</p>
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Using the graph of a function, what is a key indicator that the limit might not exist at a particular point?

<p>The function has a discontinuity or a jump at that point. (D)</p>
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If a function is continuous at a point, the limit as $x$ approaches that point always exists and is equal to the function's value at that point.

<p>True (A)</p>
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If $\lim_{x \to c^-} f(x) = L_1$ and $\lim_{x \to c^+} f(x) = L_2$, what must be true for $\lim_{x \to c} f(x)$ to exist?

<p>$L_1 = L_2$</p>
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The limit laws allow us to evaluate limits without using a ______ or ______

<p>table, graph</p>
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What does the Constant Multiple Theorem state about the limit of $k \cdot f(x)$ as $x$ approaches $c$?

<p>It is equal to $k \cdot L$, where L is the limit of f(x) as x approaches c. (B)</p>
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The Addition Theorem for limits applies only to the sum of two functions and not to their difference.

<p>False (B)</p>
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If $\lim_{x \to c} f(x) = L$ and $\lim_{x \to c} g(x) = M$, according to the Multiplication Theorem, what is $\lim_{x \to c} [f(x) \cdot g(x)]$?

<p>L * M</p>
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According to the ______ Theorem, the limit of a quotient of functions is equal to the quotient of the limits of the individual functions, provided the denominator limit is not equal to 0.

<p>Division</p>
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According to the power rule, if $\lim_{x \to c} f(x) = L$, then what is $\lim_{x \to c} (f(x))^p$ equal to?

<p>L^p (D)</p>
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The Radical/Root Theorem applies only to square roots and not to other types of roots.

<p>False (B)</p>
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When applying the Radical/Root Theorem, what condition must be met if $n$ is even?

<p>The limit of the function must be positive.</p>
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According to limit laws, $ \lim_{x \to c} k = $ ______, where k is any constant.

<p>k</p>
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Using limit theorems, evaluate $\lim_{x \to 1} (2x + 1)$.

<p>3 (B)</p>
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When evaluating the limit of a rational function, if the limit of the denominator is zero, the limit of the rational function always does not exist.

<p>False (B)</p>
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What is $\lim_{x \to 1} \sqrt{x}$?

<p>1</p>
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If $\lim_{x \to c} f(x) = 4$ then $\lim_{x \to c} (f(x))^3$ = ______.

<p>64</p>
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What is the first step in evaluating $\lim_{x \to 2} \frac{x}{x-1}$?

<p>Check the limit of the denominator. (C)</p>
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Match the limit theorems with their descriptions:

<p>Constant Multiple Theorem = The limit of a constant times a function is the constant times the limit of the function. Addition Theorem = The limit of a sum is the sum of the limits. Division Theorem = The limit of a quotient is the quotient of the limits (denominator limit not zero). Power Limit = The limit of a power of a function is the power of the limit of the function.</p>
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Which of the following is a direct application of the limit of a constant rule?

<p>$\lim_{x \to -2} 7 = 7$ (B)</p>
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If $\lim_{x \to c} f(x)$ exists, then $f(x)$ must be defined at $x = c$.

<p>False (B)</p>
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What theorem justifies splitting $\lim_{x \to a} (f(x) + g(x))$ into $\lim_{x \to a} f(x) + \lim_{x \to a} g(x)$?

<p>Addition Theorem</p>
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To directly apply the Division Theorem for limits, the limit of the ______ must not be zero.

<p>denominator</p>
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Given $\lim_{x \to 2} f(x) = 5$ and $\lim_{x \to 2} g(x) = -3$, find $\lim_{x \to 2} (2f(x) + g(x))$.

<p>7 (A)</p>
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The limit of a function as x approaches infinity can always be found by substituting infinity into the function.

<p>False (B)</p>
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What is the value of $\lim_{x \to 7} x$?

<p>7</p>
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By the constant multiple theorem,$\lim_{x \to c} -11 * f(x) = -11 * \lim_{x \to c} f(x) = -11 * L$ if $\lim_{x \to c} f(x) = $ ______.

<p>L</p>
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Given $\lim_{x \to c} f(x)= 4$ and $\lim_{x \to c} g(x) = -5$, calculate $\lim_{x \to c} f(x) + g(x)$.

<p>-1 (D)</p>
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Flashcards

What are Limits?

The backbone of calculus used to study change in detail.

What is a Limit of a Function?

A function's behavior as its variable gets close to a value.

What is L in Limit Notation?

The unique real value that f(x) approaches as x approaches c.

What is the Limit?

Denoted by L, the unique real value that f(x) will approach as x approaches c.

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What happens as x gets closer?

The values of x get closer and closer to a certain value, so do the values of f(x).

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When Does a Limit Exist?

Limits from the left and right must exist and be equal.

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What does DNE mean?

When the limit from the left does not equal the limit from the right

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What are One-Sided Limits?

Limits that consider values on only one side of c.

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What do Limit Laws enable?

Evaluate limits directly, without needing a table or graph.

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What is the limit of a constant?

The limit of a constant is the constant itself.

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Limit of a Linear Function

The limit of x as x approaches c is equal to c.

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Constant Multiple Theorem

This says that the limit of a multiple of a function is simply that multiple of the limit of the function.

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Addition Theorem

Limit of a sum of functions is the sum of the limits

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Multiplication Theorem

Limit of a product of functions is the product of their limits

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Division Theorem

Limit of the quotient is the quotient of the limits

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Power Limit

Limit of an integer power p of a function

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Radical/Root Theorem

Function with positive integer n

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What is Application of Limit Theorems?

Using Limit Theorems to Evaluate Algebraic Functions

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rational functions

Division Rule and evaluate limits of polynomial functions

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Study Notes

  • The slides contain study notes on limits and limit theorems in basic calculus
  • This note covers illustrating limits, distinguishing between limits, the theorems themselves, and applying the theorems to algebraic functions

Introduction

  • Limits are the foundation of calculus, often called "Mathematics of Change"
  • Studying limits very important for understanding change in detail
  • Evaluating a particular limit is essential for the formulation of derivatives and integrals

Limits of Functions

  • Functions of a single variable x are analyzed as x approaches a particular value c
  • The variable x can get very close to c but cannot equal c
  • The limit describes what happens to the function near that constant

Limit of a Function Using Table of Values and Graph

  • Consider a function f of a single variable x
  • Consider a constant c, which the variable x will approach
  • c may or may not be in the domain of f
  • The limit L is the unique real value that f(x) will approach as x approaches c
  • In symbols, this process is written as lim (x→c) f(x) = L
  • This reads as "The limit of f(x) as x approaches c is L"
  • Evaluating tables helps track the effect that the approach of x toward the constant has on f(x)

Example:

  • Consider lim (x→2) (1+3x)
  • f(x) = (1+3x), and the constant c is 2
  • As x approaches 2 from the left (values less than 2), f(x) approaches 7
  • As x approaches 2 from the right (values greater than 2), f(x) also approaches 7
  • Regardless of the set of values or the direction of approach, as x gets closer to 2, f(x) gets closer to 7
  • This is written symbolically as lim (x→2) (1+3x) = 7

Example 1:

  • Investigate lim (x→-1) (x² + 1) using tables of values
  • Here, c = -1 and f(x) = x² + 1
  • Approaching -1 from the left, as x gets closer to -1, f(x) approaches 2
  • Approaching -1 from the right, as x gets closer to -1, f(x) approaches 2
  • This suggests lim (x→-1) (x² + 1) = 2

Example 2:

  • Investigate lim (x→0) |x| through a table of values
  • Approaching 0 from both the left and the right, |x| approaches 0
  • Thus, lim (x→0) |x| = 0
  • f(x) = |x| in this example

Example 3:

  • Investigate lim (x→1) (x²-5x+4 / x-1) by constructing tables of values
  • Approaching 1 from the left and the right, f(x) approaches -3
  • So, lim (x→1) (x²-5x+4 / x-1) = -3

Example 4:

  • Investigate the limit through a table of values if f(x) = x+1 if x<4, and (x-4)²+3 if x ≥ 4
  • x approaches 5 from the left while it approaches 3 from the right
  • The values that f(x) approaches are not equal, and the limit does not exist (DNE)

One-Sided Limits

  • For a limit L to exist, the limits from the left and right must both exist and be equal to L
  • lim(x→c) f(x) DNE whenever lim(x→c⁻) f(x) ≠ lim(x→c⁺) f(x)
  • Limits are referred to as one-sided limits

Limit Theorems

  • Limit laws can be used to directly evaluate limits without needing a table or graph
  • Let c be a constant, and f and g be functions that may or may not have c in their domains

Limit of a Constant

  • The limit of a constant is the constant itself
  • If k is any constant, then lim (x→c) k = k

Limit of a Linear Function

  • The limit of x as x approaches c is equal to c
  • This can be thought of as the substitution law because x is simply substituted by c

Constant Multiple Theorem

  • The limit of a multiple of a function is simply that multiple of the limit of the function
  • lim (x→c) k * f(x) = k * lim (x→c) f(x) = k * L

The Addition Theorem

  • The limit of a sum of functions is the sum of the limits of the individual functions
  • This includes subtraction within its laws
  • In symbols, lim (x→c) (f(x) + g(x)) = lim (x→c) f(x) + lim (x→c) g(x) = L + M
  • lim (x→c) (f(x) - g(x)) = lim (x→c) f(x) - lim (x→c) g(x) = L - M

Multiplication Theorem

  • Similar to the addition theorem, but with multiplication replacing addition
  • The limit of a product of functions equals the product of their limits
  • lim (x→c) (f(x) * g(x)) = lim (x→c) f(x) * lim (x→c) g(x) = L * M

Division Theorem

  • The limit of a quotient of function is equal to the quotient of the limits
  • The denominator's limit is not equal to zero
  • In symbols: lim (x→c) f(x)/g(x) = lim (x→c) f(x) / lim (x→c) g(x) = L/M, provided M≠ 0

The Power Limit

  • The limit of an integer power p of a function is just that power of the limit of a function
  • lim (x→c) (f(x))^p = (lim (x→c) f(x))^p = L^p

The Radical/Root Theorem

  • If n is a positive integer, the limit of the nth root of a function is just the nth root of the limit
  • Provided that nth root of the limit is a real number
  • If n is even, the limit of the function must be positive

Application of Limit Theorems

  • Limit theorems can evaluate algebraic functions

Limits of Polynomial Functions

  • Polynomial functions can be evaluated using limit theorems

Limits of Rational Functions

  • Limit theorems are applied when evaluating rational functions
  • Theorem 1, the Division Rule, must be recalled

Limits of Radical Functions

  • Radical functions are evaluated using limit theorems

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