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Ch. 5 - Integration
Briggs - Calculus: Early Transcendentals 3rd Edition
Briggs3rd EditionCalculus: Early TranscendentalsISBN: 9780136847243당신이 사용하는 게 아니라요?교과서 변경
5장, 문제 5.3.107d

Explain why or why not Determine whether the following statements are true and give an explanation or counterexample.                                                                          
                                                                                                                                                                                     (d) If A(𝓍) = 3𝓍²― 𝓍― 3 is an area function for ƒ, then                                                                                                                                   
     B(𝓍) = 3𝓍² ― 𝓍 is also an area function for ƒ.

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Recall that an area function for a function \( f \) is defined as \( A(x) = \int_a^x f(t) \, dt \) for some fixed lower limit \( a \). The key property is that the derivative of the area function equals the original function, i.e., \( A'(x) = f(x) \).
Given \( A(x) = 3x^2 - x - 3 \), find its derivative to identify \( f(x) \). Using the power rule, \( A'(x) = \frac{d}{dx}(3x^2) - \frac{d}{dx}(x) - \frac{d}{dx}(3) = 6x - 1 - 0 = 6x - 1 \). So, \( f(x) = 6x - 1 \).
Next, check the function \( B(x) = 3x^2 - x \). Find its derivative: \( B'(x) = \frac{d}{dx}(3x^2) - \frac{d}{dx}(x) = 6x - 1 \). Notice that \( B'(x) = f(x) \) as well.
Since both \( A(x) \) and \( B(x) \) have the same derivative \( f(x) = 6x - 1 \), they differ by a constant. To confirm if \( B(x) \) is also an area function for \( f \), check the difference \( A(x) - B(x) = (3x^2 - x - 3) - (3x^2 - x) = -3 \), which is a constant.
Therefore, \( B(x) \) can also serve as an area function for \( f \) because area functions differ by a constant. This aligns with the Fundamental Theorem of Calculus, which states that any two antiderivatives of the same function differ by a constant.

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주요 개념

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Area Function and the Fundamental Theorem of Calculus

An area function A(x) for a function f is defined as the integral of f from a fixed point to x. According to the Fundamental Theorem of Calculus, the derivative of this area function A'(x) equals the original function f(x). This relationship is key to verifying if a given function is an area function for f.
추천 영상:
가이드 코스
05:22
Fundamental Theorem of Calculus Part 2

Derivative of a Polynomial Function

To check if a function is an area function for f, differentiate it and compare the result to f. Differentiation of polynomials involves applying power rules term-by-term. For example, the derivative of 3x² - x - 3 is 6x - 1, which must match f(x) for the function to be an area function.
추천 영상:
07:00
Taylor Polynomials

Effect of Constant Terms on Area Functions

Adding or subtracting a constant to an area function does not change its derivative, so it remains an area function for the same f. This means if A(x) is an area function for f, then A(x) + C, where C is any constant, is also an area function for f.
추천 영상:
05:06
Finding Area When Bounds Are Not Given
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교과서 질문

Properties of integrals Consider two functions ƒ and g on [1,6] such that ∫₁⁶ƒ(𝓍) d𝓍 = 10 and ∫₁⁶g(𝓍) d𝓍 = 5, ∫₄⁶ƒ(𝓍) d𝓍 = 5 , and ∫₁⁴g(𝓍) d𝓍 = 2. Evaluate the following integrals.


(d) ∫₄⁶ (g(𝓍) ― f(𝓍) d𝓍

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교과서 질문

Properties of integrals Use only the fact that ∫₀⁴ 3𝓍 (4 ―𝓍) d𝓍 = 32, and the definitions and properties of integrals, to evaluate the following integrals, if possible.

(d) ∫₀⁸ 3𝓍(4 ― 𝓍) d(𝓍)

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교과서 질문

Use Table 5.6 to evaluate the following indefinite integrals.                                                                                                               

                                                                                                                                                                  

 (d) ∫ cos 𝓍/7 d𝓍

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교과서 질문

Area functions The graph of ƒ is shown in the figure. Let A(x) = ∫₀ˣ ƒ(t) dt and F(x) = ∫₂ˣ ƒ(t) dt be two area functions for ƒ. Evaluate the following area functions.

(d) F(8)

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교과서 질문

Sigma notation Express the following sums using sigma notation. (Answers are not unique.)

(d) 1 + 1/2 + 1/3 + 1/4

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교과서 질문

Sigma notation Evaluate the following expressions.

(d)     5                                                                                                                                                                              

       ∑ (1 + n²)                                                                                                                                                                          

       n=1                         

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