Chapter 1: Problem 11
If \(y=u^{3}+5\) and \(u=x^{2}-1,\) find \(\left.\frac{d y}{d x}\right|_{x=1}\).
Short Answer
Expert verified
\(\frac{dy}{dx}|_{x=1} = 0.\)
Step by step solution
01
Identify the Functions
We have the function for \(y\) given as \(y = u^3 + 5\) and another function for \(u\) given as \(u = x^2 - 1\). Our goal is to find \(\frac{dy}{dx}\).
02
Use the Chain Rule
Since \(y\) is a function of \(u\) and \(u\) is a function of \(x\), we use the chain rule to find \(\frac{dy}{dx}\). The chain rule states that \(\frac{dy}{dx} = \frac{dy}{du} \cdot \frac{du}{dx}\).
03
Differentiate \(y\) with respect to \(u\)
Differentiate \(y = u^3 + 5\) with respect to \(u\). \[ \frac{dy}{du} = 3u^2. \]
04
Differentiate \(u\) with respect to \(x\)
Differentiate \(u = x^2 - 1\) with respect to \(x\). \[ \frac{du}{dx} = 2x. \]
05
Compute \(\frac{dy}{dx}\)
Multiply the derivatives from Step 3 and Step 4 to find \(\frac{dy}{dx}\). \[ \frac{dy}{dx} = \frac{dy}{du} \cdot \frac{du}{dx} = 3u^2 \cdot 2x = 6xu^2. \]
06
Substitute \(u = x^2 - 1\)
Replace \(u\) with \(x^2 - 1\) in the expression for \(\frac{dy}{dx}\): \[ \frac{dy}{dx} = 6x(x^2 - 1)^2. \]
07
Evaluate at \(x=1\)
Substitute \(x = 1\) into the expression \(\frac{dy}{dx} = 6x(x^2 - 1)^2\). When \(x = 1\), \(u = (1)^2 - 1 = 0\). Therefore:\[ \frac{dy}{dx} = 6\times 1 \times (0)^2 = 0. \]
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Differentiation
Differentiation is a core concept in calculus that refers to the process of finding the derivative of a function. In simpler terms, a derivative measures how a function changes as its input changes. It is a vital tool for understanding how different quantities are related to each other. For example, finding the rate at which a car accelerates down a road. When you differentiate a function, you are essentially calculating the slope of the function at any given point. This slope tells us how fast the function is changing at that point.
- The derivative of a function is denoted by \(\frac{dy}{dx}\) if the function is expressed as \(y = f(x)\).
- The process involves applying rules such as the power rule, product rule, quotient rule, and chain rule.
Calculus Problem Solving
Solving calculus problems often involves a combination of theoretical understanding and practical step-by-step approaches. The chain rule is just one of many tools a calculus student can use to solve complex differentiation problems when involving composite functions.Here's how calculus problem solving typically unfolds:
- Understand the problem: Clearly identify what you are required to find. In the given exercise, we are tasked with finding \(\frac{dy}{dx}\).
- Break down into manageable parts: Identify individual functions or expressions (like \(y = u^3 + 5\) and \(u = x^2 - 1\)). Sort out main elements before applying rules.
- Apply calculus concepts: Use rules and formulas such as derivatives and integrals to tackle each part navigated by understanding differentiations methods.
Function Composition
Function composition involves creating a complex function by combining two or more simpler functions. In mathematical terms, if you have a function \(g(x)\) and another function \(f(u)\), composing them results in a function like \(f(g(x))\), which means you apply \(g\) and then \(f\).For our problem, we have:
- \(u = x^2 - 1\): a function of \(x\).
- \(y = u^3 + 5\): a function of \(u\)