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Ch. 3 - Derivatives
Hass - Thomas' Calculus 15th Edition
Hass15th EditionThomas' CalculusISBN: 9780137616077당신이 사용하는 게 아니라요?교과서 변경
3장, 문제 3.6.63

Second Derivatives


Find y'' in Exercises 59–64.


y = x(2x + 1)⁴

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1
First, identify the function y = x(2x + 1)^4. We need to find the second derivative y''.
To find the first derivative y', apply the product rule. The product rule states that if you have a function y = u(x)v(x), then y' = u'(x)v(x) + u(x)v'(x). Here, let u(x) = x and v(x) = (2x + 1)^4.
Calculate the derivatives: u'(x) = 1 and v'(x) using the chain rule. For v(x) = (2x + 1)^4, let w = 2x + 1, then v(x) = w^4. The derivative v'(x) = 4w^3 * (dw/dx) = 4(2x + 1)^3 * 2.
Substitute the derivatives back into the product rule: y' = 1 * (2x + 1)^4 + x * 8(2x + 1)^3.
Simplify y' and then find the second derivative y'' by differentiating y' again. Use the product rule and chain rule as necessary to find y''.

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주요 개념

질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.

Product Rule

The product rule is a fundamental differentiation rule used when finding the derivative of a product of two functions. If you have two functions u(x) and v(x), the derivative of their product is given by u'(x)v(x) + u(x)v'(x). This rule is essential for differentiating expressions like y = x(2x + 1)⁴, where x is multiplied by another function.
추천 영상:
05:18
The Product Rule

Chain Rule

The chain rule is used to differentiate composite functions, where one function is nested inside another. If you have a function y = f(g(x)), the derivative is f'(g(x)) * g'(x). In the given problem, the chain rule helps differentiate the term (2x + 1)⁴, treating it as a composite function with an inner function g(x) = 2x + 1.
추천 영상:
05:02
Intro to the Chain Rule

Second Derivative

The second derivative, denoted as y'', is the derivative of the first derivative y'. It provides information about the curvature or concavity of the function's graph. Calculating the second derivative involves differentiating the first derivative, often requiring the application of differentiation rules like the product and chain rules multiple times.
추천 영상:
06:02
The Second Derivative Test: Finding Local Extrema