/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 66 In Exercises \(65-70,\) find the... [FREE SOLUTION] | 91Ó°ÊÓ

91Ó°ÊÓ

In Exercises \(65-70,\) find the value of \((f \circ g)^{\prime}\) at the given value of \(x .\) $$f(u)=1-\frac{1}{u}, \quad u=g(x)=\frac{1}{1-x}, \quad x=-1$$

Short Answer

Expert verified
The value of \((f \circ g)'\) at \(x = -1\) is 1.

Step by step solution

01

Understand the Composition of Functions

We are given two functions, \( f(u) = 1 - \frac{1}{u} \) and \( g(x) = \frac{1}{1-x} \). The function \( (f \circ g)(x) \) means that we substitute \( g(x) \) into \( f(u) \). Therefore, \( (f \circ g)(x) = f(g(x)) = 1 - \frac{1}{g(x)} = 1 - \left( 1 - x \right) \).
02

Simplify the Composite Function

Let's simplify the expression. Since \( g(x) = \frac{1}{1-x} \), then \( \frac{1}{g(x)} = 1 - x \). Substituting this back into \( f \), the composition becomes \( f(g(x)) = 1 - (1 - x) = x \). So \( (f \circ g)(x) = x \).
03

Differentiate the Composite Function

Now, we need to find the derivative of \( (f \circ g)(x) = x \). Clearly, the derivative \( \frac{d}{dx}[x] = 1 \).
04

Evaluate the Derivative at the Given Value

We are asked to find \( (f \circ g)'(-1) \). Here, \( (f \circ g)'(x) = 1 \) for all \( x \). Therefore, \( (f \circ g)'(-1) = 1 \).

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Over 30 million students worldwide already upgrade their learning with 91Ó°ÊÓ!

Key Concepts

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

Chain Rule
The Chain Rule is a fundamental concept in calculus that helps us differentiate compositions of functions. When you have two functions, say \( f(u) \) and \( g(x) \), and you need to find the derivative of their composition \( (f \circ g)(x) = f(g(x)) \), the chain rule is your go-to tool. It states that the derivative of composed functions \( f(g(x)) \) is the derivative of \( f \) with respect to \( u \) (\( f'(u) \)) times the derivative of \( g \) with respect to \( x \) (\( g'(x) \)). This gives:
  • \( \frac{d}{dx}[f(g(x))] = f'(g(x)) \cdot g'(x) \)
In our problem, we didn't get to apply the chain rule in the traditional sense because the function simplified neatly to \( x \). However, understanding how the chain rule works would prepare you to handle more complex compositions. It's crucial to identify the inner function \( g(x) \) and the outer function \( f(u) \), then differentiate each appropriately when the composition doesn't simplify immediately.
Derivative Calculation
Calculating the derivative involves finding the rate at which a function changes with respect to a variable. In straightforward cases, like our simplified composite function \( (f \circ g)(x) = x \), the derivative is easy. Derivatives show how a function increases or decreases. For linear functions such as \( y = x \), the derivative is the coefficient of \( x \), which is \( 1 \). https://latex.codecogs.com/svg.latex?\frac{d}{dx}[x] = 1.
Derivatives become more important when dealing with polynomials, exponential and trigonometric functions. Each function type has its differentiation rules, like the power rule for polynomials. For composite functions where simplification is not possible, the Chain Rule allows us to handle them by breaking down the differentiation process into smaller, manageable steps.
Function Simplification
Function simplification is the process of transforming a function into its simplest form to make calculations easier. In the given exercise, simplifying the composition \( (f \circ g)(x) \) was essential. Initially, \( (f \circ g)(x) \) looks complicated:
  • \( f(g(x)) = 1 - \frac{1}{g(x)} \)
  • Where \( g(x) = \frac{1}{1-x} \),
simplifying gives us \( f(g(x)) = x \).
Many mathematical problems become easier when we reduce complex forms. Simplification can involve expanding, factoring, or canceling terms to reduce the burden of calculation. It's a helpful step before proceeding with operations like differentiation or integration. Always look out for algebraic opportunities to simplify expressions. This practice makes solutions clearer and computations less prone to errors.

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Most popular questions from this chapter

Quadratic approximations $$ \begin{array}{l}{\text { a. Let } Q(x)=b_{0}+b_{1}(x-a)+b_{2}(x-a)^{2} \text { be a quadratic }} \\ {\text { approximation to } f(x) \text { at } x=a \text { with the properties: }}\end{array} $$ $$ \begin{aligned} \text { i) } Q(a) &=f(a) \\ \text { ii) } Q^{\prime}(a) &=f^{\prime}(a) \\ \text { iii) } Q^{\prime \prime}(a) &=f^{\prime \prime}(a) \end{aligned} $$ $$ \text{Determine the coefficients}b_{0}, b_{1}, \text { and } b_{2} $$ $$ \begin{array}{l}{\text { b. Find the quadratic approximation to } f(x)=1 /(1-x) \text { at }} \\ {\quad x=0 .} \\ {\text { c. } \operatorname{Graph} f(x)=1 /(1-x) \text { and its quadratic approximation at }} \\ {x=0 . \text { Then zoom in on the two graphs at the point }(0,1) \text { . }} \\ {\text { Comment on what you see. }}\end{array} $$ $$ \begin{array}{l}{\text { d. Find the quadratic approximation to } g(x)=1 / x \text { at } x=1} \\ {\text { Graph } g \text { and its quadratic approximation together. Comment }} \\ {\text { on what you see. }}\end{array} $$ $$ \begin{array}{l}{\text { e. Find the quadratic approximation to } h(x)=\sqrt{1+x} \text { at }} \\ {x=0 . \text { Graph } h \text { and its quadratic approximation together. }} \\ {\text { Comment on what you see. }} \\\ {\text { f. What are the linearizations of } f, g, \text { and } h \text { at the respective }} \\ {\text { points in parts (b), (d), and (e)? }}\end{array} $$

Chain Rule Suppose that \(f(x)=x^{2}\) and \(g(x)=|x| .\) Then the composites $$(f \circ g)(x)=|x|^{2}=x^{2} \quad\( and \)\quad(g \circ f)(x)=\left|x^{2}\right|=x^{2}$$ are both differentiable at \(x=0\) even though \(g\) itself is not differentiable at \(x=0 .\) Does this contradict the Chain Rule? Explain.

Use a CAS to perform the following steps. \begin{equation} \begin{array}{l}{\text { a. Plot the equation with the implicit plotter of a CAS. Check to }} \\ {\text { see that the given point } P \text { satisfies the equation. }} \\ {\text { b. Using implicit differentiation, find a formula for the deriva- }} \\ {\text { tive } d y / d x \text { and evaluate it at the given point } P .}\end{array} \end{equation} \begin{equation} \begin{array}{l}{\text { c. Use the slope found in part (b) to find an equation for the tan- }} \\ {\text { gent line to the curve at } P \text { . Then plot the implicit curve and }} \\ {\text { tangent line together on a single graph. }}\end{array} \end{equation} \begin{equation} x+\tan \left(\frac{y}{x}\right)=2, \quad P\left(1, \frac{\pi}{4}\right) \end{equation}

Graph \(y=3 x^{2}\) in a window that has \(-2 \leq x \leq 2,0 \leq y \leq 3\) Then, on the same screen, graph $$y=\frac{(x+h)^{3}-x^{3}}{h}$$ for \(h=2,1,0.2 .\) Then try \(h=-2,-1,-0.2 .\) Explain what is going on.

The derivative of \(\cos \left(x^{2}\right) \quad\) Graph \(y=-2 x \sin \left(x^{2}\right)\) for \(-2 \leq\) \(x \leq 3 .\) Then, on the same screen, graph $$y=\frac{\cos \left((x+h)^{2}\right)-\cos \left(x^{2}\right)}{h}$$ for \(h=1.0,0.7,\) and \(0.3 .\) Experiment with other values of \(h .\) What do you see happening as \(h \rightarrow 0 ?\) Explain this behavior.

See all solutions

Recommended explanations on Math Textbooks

View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

Study anywhere. Anytime. Across all devices.