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In Exercises 25 through \(32,\) use the quotient rule to find \(\frac{d y}{d u}\). $$ y=\frac{-4 \ln u}{u^{4}+3} $$

Short Answer

Expert verified
The derivative \( \frac{d y}{d u} \) is \( \frac{16u^3 \ln u - 4u^3 - \frac{12}{u}}{(u^4 + 3)^2} \)."

Step by step solution

01

Identify the functions

The function given is a quotient function \( y = \frac{-4 \ln u}{u^4 + 3} \), which consists of a numerator \( f(u) = -4 \ln u \) and a denominator \( g(u) = u^4 + 3 \).
02

Recall the Quotient Rule

The quotient rule states that if you have a function \( y = \frac{f(u)}{g(u)} \), then its derivative is \( \frac{d y}{d u} = \frac{f'(u)g(u) - f(u)g'(u)}{(g(u))^2} \).
03

Calculate \( f'(u) \)

The derivative of the numerator \( f(u) = -4 \ln u \) is \( f'(u) = \frac{-4}{u} \), because the derivative of \( \ln u \) is \( \frac{1}{u} \).
04

Calculate \( g'(u) \)

The derivative of the denominator \( g(u) = u^4 + 3 \) is \( g'(u) = 4u^3 \), using the power rule which multiplies the exponent by the coefficient and reduces the exponent by one.
05

Apply the Quotient Rule

Substitute \( f(u), f'(u), g(u), \) and \( g'(u) \) into the quotient rule: \[ \frac{d y}{d u} = \frac{\left(\frac{-4}{u}\right)(u^4 + 3) - (-4 \ln u)(4u^3)}{(u^4 + 3)^2} \].
06

Simplify the Derivative Expression

Simplify the expression: First part: \( \frac{-4u^4}{u} - \frac{4 \cdot 3}{u} = -4u^3 - \frac{12}{u} \). Second part: \(-4 \cdot 4 \ln u \cdot u^3 = -16 u^3 \ln u \). Combine these to form the numerator: \(-4u^3 - \frac{12}{u} + 16 u^3 \ln u \).
07

Reorganize and Combine Terms

Combine and reorganize terms: The final expression for \( \frac{d y}{d u} \) is \( \frac{[16u^3 \ln u - 4u^3 - \frac{12}{u}]}{(u^4 + 3)^2} \).

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Derivative Calculation
Calculating derivatives can sometimes seem daunting, but understanding the basics behind each step can make the task much simpler. In this exercise, we are working with a quotient function, specifically the function y = \(-4 \ln u / (u^4 + 3)\). Understanding how to differentiate a quotient using the Quotient Rule is essential here.

To find the derivative of a quotient, the Quotient Rule comes in handy. It allows us to calculate the derivative of a function that is the division of two other functions. Mathematically, the Quotient Rule can be expressed as:
  • If \( y = \frac{f(u)}{g(u)} \), then \( \frac{dy}{du} = \frac{f'(u)g(u) - f(u)g'(u)}{(g(u))^2} \)
Understanding this formula is key. First, you find the derivatives of the numerator \( f(u) \) and the denominator \( g(u) \). Then, plug these values into the Quotient Rule formula. This requires careful attention to signs and operations to ensure accuracy.

In this exercise, once you identify \( f(u) = -4 \ln u \) and \( g(u) = u^4 + 3 \), calculating each derivative step-by-step ensures that the overall derivative is computed correctly. Remember, a strong grasp on how to apply the Quotient Rule streamlines the process of deriving expressions.
Calculus Exercise
Approaching a calculus exercise like this one requires methodical thinking. The given problem requires us to differentiate a function using the Quotient Rule, and it involves several steps starting with clear function identification.

When looking at the given function, y = \(-4 \ln u / (u^4 + 3)\), it's important to clarify that the term \(-4 \ln u\) captures a logarithmic concept, while the bottom, \( u^4 + 3\), incorporates polynomial behavior.

Breaking the problem down further, using the derivatives of individual sections by applying rules such as the power rule and the natural logarithm rule, simplifies the challenge. Here, identifying \( f(u) = -4 \ln u \) and recognizing that its derivative involves a relatively straightforward application of the logarithmic derivative \( \left(f'(u) = -\frac{4}{u}\right)\), helps streamline the process.

Meanwhile, the denominator's derivative resorts to the power rule \( \left(g'(u) = 4u^3\right)\), which is also fairly direct. Understanding these derivative calculation techniques is pivotal in successfully tackling calculus exercises. Each derivative calculation reflects typical challenges encountered during calculus problem-solving, necessitating a solid grasp on fundamentals.
Simplifying Expressions
After successfully applying the quotient rule, simplification becomes the next essential step. This ensures that the derived expression is manageable and represents the solution accurately.

Upon setting up the quotient's derivative, \( \frac{d y}{d u} = \frac{\left(\frac{-4}{u}\right)(u^4 + 3) - (-4 \ln u)(4u^3)}{(u^4 + 3)^2} \), it's important to simplify for conciseness and clarity. Reworking such expressions involves distributing numerators and combining like terms.

Firstly, focus on distributing terms individually:
  • The first term simplifies to \(-4u^3 - \frac{12}{u}\)
  • The second term results in \(-16 u^3 \ln u\)
Compilation of these yields:\(-4u^3 - \frac{12}{u} + 16 u^3 \ln u\)

Simplifying often requires multiple stages, including rearranging terms and checking for common factors. Reducing complexity in mathematical expressions is crucial for clearer interpretation, enhancing comprehension and communication of results in calculus and beyond.

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