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Questions and Answers
What is the condition for the limit to exist when defining the infinite sum?
What is the condition for the limit to exist when defining the infinite sum?
For all values of |q| greater than 1, the limit of q^n does not go to zero as n approaches infinity.
For all values of |q| greater than 1, the limit of q^n does not go to zero as n approaches infinity.
True
What does the continuity of a function on an interval imply regarding its graph?
What does the continuity of a function on an interval imply regarding its graph?
The graph can be drawn without lifting the pencil off the paper.
The definitions of continuity are equivalent when the limits satisfy the criteria for ______.
The definitions of continuity are equivalent when the limits satisfy the criteria for ______.
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Match the term with its description regarding continuity:
Match the term with its description regarding continuity:
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Using the Binomial formula, which term indicates that q < 1?
Using the Binomial formula, which term indicates that q < 1?
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All functions studied previously are continuous.
All functions studied previously are continuous.
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What is the relationship between the value of q and the limit of q^n as n approaches infinity?
What is the relationship between the value of q and the limit of q^n as n approaches infinity?
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What is the second point chosen to find the tangent line for the function f(x) = x^3 near x = 2?
What is the second point chosen to find the tangent line for the function f(x) = x^3 near x = 2?
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The equation of a tangent line can be written using only one point on the function.
The equation of a tangent line can be written using only one point on the function.
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What is the value of f(2) for the function f(x) = x^3?
What is the value of f(2) for the function f(x) = x^3?
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The equation of the tangent line at x = 2 is given by ŷ = _____ · x̂ - 30.
The equation of the tangent line at x = 2 is given by ŷ = _____ · x̂ - 30.
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Match the following values to their corresponding points on the function f(x) = x^3:
Match the following values to their corresponding points on the function f(x) = x^3:
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What is the purpose of finding a tangent line to the graph of a function?
What is the purpose of finding a tangent line to the graph of a function?
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The function f(x) = x^3 is continuous everywhere.
The function f(x) = x^3 is continuous everywhere.
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What is the slope of the tangent line calculated using the points (2, 8) and (3, 27)?
What is the slope of the tangent line calculated using the points (2, 8) and (3, 27)?
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What is the limit value as n approaches infinity of the expression $\frac{x_n^3 - 8}{x_n - 2}$ when $x_n$ approaches 2?
What is the limit value as n approaches infinity of the expression $\frac{x_n^3 - 8}{x_n - 2}$ when $x_n$ approaches 2?
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The expression $\frac{x_n^3 - 8}{x_n - 2}$ directly equals $x_n^2 + 2x_n + 4$ at $x_n = 2$.
The expression $\frac{x_n^3 - 8}{x_n - 2}$ directly equals $x_n^2 + 2x_n + 4$ at $x_n = 2$.
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What does $k_n$ converge to as $x_n$ approaches 2 in the linear approximation example?
What does $k_n$ converge to as $x_n$ approaches 2 in the linear approximation example?
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The derivative is defined for a function $f: D \rightarrow \mathbb{R}$ if certain limits exist at points _____ and _____ within the domain.
The derivative is defined for a function $f: D \rightarrow \mathbb{R}$ if certain limits exist at points _____ and _____ within the domain.
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Match the following expressions to their corresponding components in the example.
Match the following expressions to their corresponding components in the example.
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Which of the following expressions represent the dependent relationship of $x_n$?
Which of the following expressions represent the dependent relationship of $x_n$?
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As $x_n$ approaches 2, the term $(x_n - 2)^2$ tends to zero.
As $x_n$ approaches 2, the term $(x_n - 2)^2$ tends to zero.
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What type of function does the expression $y = \frac{x_n^3 - 8}{x_n - 2}$ approximate?
What type of function does the expression $y = \frac{x_n^3 - 8}{x_n - 2}$ approximate?
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What must a function be if it is differentiable at a point?
What must a function be if it is differentiable at a point?
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The Squeeze Theorem is applied to prove that if a function is differentiable, it converges to zero.
The Squeeze Theorem is applied to prove that if a function is differentiable, it converges to zero.
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What is the formula provided by the Product Rule for differentiation?
What is the formula provided by the Product Rule for differentiation?
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If two functions f and g are differentiable at point x, their product (f · g) is also ______ at that point.
If two functions f and g are differentiable at point x, their product (f · g) is also ______ at that point.
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Match the terms with their definitions:
Match the terms with their definitions:
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Which statement about the continuity of differentiable functions is true?
Which statement about the continuity of differentiable functions is true?
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For arbitrary sequence (x_n) such that x_n → x, we can say that ______ is an important aspect of differentiability.
For arbitrary sequence (x_n) such that x_n → x, we can say that ______ is an important aspect of differentiability.
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The limit lim |f'(x) · (x_n - x)| + |x_n - x| approaches zero as n approaches infinity.
The limit lim |f'(x) · (x_n - x)| + |x_n - x| approaches zero as n approaches infinity.
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What is the derivative of $x^2$?
What is the derivative of $x^2$?
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The derivative of $ rac{1}{x}$ is $- rac{1}{x^2}$.
The derivative of $ rac{1}{x}$ is $- rac{1}{x^2}$.
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What is the general formula for deriving $x^{k+1}$?
What is the general formula for deriving $x^{k+1}$?
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The derivative of $(x^3)'$ is _____.
The derivative of $(x^3)'$ is _____.
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Match the following derivatives with their functions:
Match the following derivatives with their functions:
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Which theorem is used to calculate the derivative of a natural power of $x$?
Which theorem is used to calculate the derivative of a natural power of $x$?
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The function $f(x) = rac{1}{x}$ is not differentiable at $x = 0$.
The function $f(x) = rac{1}{x}$ is not differentiable at $x = 0$.
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What is the derivative of $x$, denoted as $(x)'$?
What is the derivative of $x$, denoted as $(x)'$?
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What does the notation f ′ (x) represent?
What does the notation f ′ (x) represent?
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The derivative of a function exists if the limit does not depend on the choice of sequence xn.
The derivative of a function exists if the limit does not depend on the choice of sequence xn.
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What is required for a function to be differentiable at point x?
What is required for a function to be differentiable at point x?
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The derivative f ′ (x) is defined using the limit of the expression ___ as n approaches infinity.
The derivative f ′ (x) is defined using the limit of the expression ___ as n approaches infinity.
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Which of the following statements about differentiability is true?
Which of the following statements about differentiability is true?
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A function must be defined on an interval (a, b) to have a derivative at point x.
A function must be defined on an interval (a, b) to have a derivative at point x.
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Match the following terms with their definitions:
Match the following terms with their definitions:
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For the derivative to exist at point x, the limit must approach the same ___ independently of the choice of sequence.
For the derivative to exist at point x, the limit must approach the same ___ independently of the choice of sequence.
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Study Notes
Lecture 4: Mathematical Methods in Economics and Finance
-
Topic Outline:
- Limits and infinite sums
- Continuity of a function
- Derivative of a function
- Composition of functions (next lecture)
Limits of Sequences
- Definition: A number x is the limit of a sequence (an) if, for any ε > 0, there exists a natural number N such that for all n > N, |an - x| < ε. In this case, the sequence converges.
- Infinite Limits: A sequence (an) tends to infinity if, for any M, there exists N ∈ N such that for all n > N, an > M. A sequence tends to minus infinity similarly, with an < M for all n > N.
- Finite Limits Theorem: A sequence of real numbers has at most one finite limit. This generalizes to infinite limits as well.
Arithmetic Properties of Limits
- Theorem L3.2 (Sum): If sequences (an) and (bn) have finite limits, then (an + bn) also has a finite limit; moreover, lim (an + bn) = lim an + lim bn
- Theorem L3.3 (Product): If sequences (an) and (bn) have finite limits, then (anbn) also has a finite limit; moreover, lim (anbn) = lim an • lim bn
- Theorem L3.4 (Quotient): If sequences (an) and (bn) have finite limits, and lim bn ≠ 0, then (an/bn) also has a finite limit; moreover, lim (an/bn) = lim an / lim bn
Infinite Sums
- Definition: Given a sequence aj, the infinite sum Σj=1∞ aj is defined as the limit limn→∞ Σj=1n aj, if this limit exists.
Infinite Sums - Example
- Example 1: Consider Σj=0∞ qj, where 0 < |q| < 1. The sum is equal to 1/(1 - q), when |q| < 1.
Squeeze Theorem for Sequences
- Theorem L4.1 (Squeeze Theorem): If an ≤ bn ≤ cn for all n ∈ N, and lim an = lim cn = x, then lim bn = x.
Continuity of Functions
- Definition: A function f : D → R is continuous at a point x ∈ (a, b) if for any sequence (xn) of real numbers such that xn → x, there exists limn→∞ f(xn) and limn→∞ f(xn)=f(x).
- Alternative Definition: A function f : D → R is continuous at x ∈ (a, b) if, for any ε > 0, there exists a δ > 0 such that |f(z) - f(x)| < ε for all z such that |z - x| < δ.
Continuity of Functions (Geometric Interpretation)
- Geometrically, continuity means the graph of the function can be drawn without lifting the pen.
Derivatives
- Definition: The derivative of a function f at a point x is defined as f'(x) = limxn→x (f(xn)-f(x))/(xn-x) , given that the limit exists.
Derivative of a Linear Function
- Definition: f(x) = ax + b is differentiable at any point x for all real values of x and f'(x) = a
Derivative of xk
- Theorem L4.3: The function f(x) = xk, where k ∈ N is differentiable and f'(x) = kxk-1.
- Proof: Uses the Binomial Theorem to evaluate the limit.
Additivity of the Derivative
- Theorem L4.4: The sum of two differentiable functions is also differentiable, and its derivative is the sum of the derivatives of the two functions: (f+g)'(x) = f'(x) + g'(x)
Differentiability Implies Continuity
- Theorem L4.5: If a function is differentiable at a point, then it is continuous at that point.
Product Rule for Differentiation
- Theorem L4.6: The derivative of the product of two functions is given by (fg)'(x) = f'(x)g(x) + f(x)g'(x).
Corollary (Constant Multiple Rule)
- For any constant c ∈ R and differentiable function f, the derivative of c·f(x) is given by (cf)'(x) = c·f'(x)
Additional Information (Examples)
- Derivatives are shown for polynomial functions (x3 and higher orders) and for 1/x.
- The slides cover composition of functions and related properties.
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Description
This quiz covers the key concepts discussed in Lecture 4 on Mathematical Methods in Economics and Finance. Topics included are limits and infinite sums, continuity, derivatives, and sequence limits. Understand the fundamental principles that apply to sequences and their limits within economic contexts.
