/*! 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 86 If \(f(x)\) is a function, then ... [FREE SOLUTION] | 91Ó°ÊÓ

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If \(f(x)\) is a function, then \((f \circ f)(x)=f(f(x))\) is the composition of \(f\) with itself. This is called an iterated function, and the composition can be repeated many times. For example, \((f \circ f \circ f)(x)=f(f(f(x))) .\) Iterated functions are very useful in many areas, including finance (compound interest is \(a\) simple case) and the sciences (in weather forecasting, for example). For the each function, use the Chain Rule to find the derivative. If \(f(x)=x^{2}+1,\) find \(\frac{d}{d x}[(f \circ f)(x)]\).

Short Answer

Expert verified
\(\frac{d}{dx}[(f \circ f)(x)] = 4x^3 + 4x\)

Step by step solution

01

Understand the given function

The given function is an iterated function: ewline ewline \((f \circ f)(x) = f(f(x))\).
02

Substitute the function into itself

Let's substitute the given function \(f(x)\) into itself: \(f(x) = x^2 + 1\) and ewline ewline then, \((f \circ f)(x) = f(f(x)) = f(x^2 + 1)\).
03

Compute \(f(x^2 + 1)\)

Next, compute what \(f(x^2 + 1)\) is by substituting \(x^2 + 1\) into the function \(f\): \(f(x^2 + 1) = (x^2 + 1)^2 + 1\).
04

Simplify \(f(x^2 + 1)\)

Now, expand and simplify \(f(x^2 + 1)\): \((x^2 + 1)^2 + 1 = x^4 + 2x^2 + 1 + 1 = x^4 + 2x^2 + 2\).
05

Differentiate \((f \circ f)(x)\)

Use the power rule to differentiate \((f \circ f)(x) = x^4 + 2x^2 + 2\) with respect to \(x\): newline ewline The derivative is: \(\frac{d}{dx}[x^4 + 2x^2 + 2] = 4x^3 + 4x\).

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Key Concepts

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

composition of functions
In mathematics, the composition of functions is a fundamental concept. When you have two functions, say \( f(x) \) and \( g(x) \), the composition \( (f \circ g)(x) \) means you first apply \( g \) to \( x \), and then apply \( f \) to the result of \( g(x) \). This can be written as \( f(g(x)) \). For our exercise, we are dealing with an iterated function, where a function is composed with itself: \( (f \circ f)(x) \). This means we take \( f(x) \) and then apply \( f \) again on the result of \( f(x) \).

For our given function \( f(x) = x^2 + 1 \), the iterated function \( (f \circ f)(x) \) results in \( f(f(x)) \). Understanding function composition is key in dealing with more complex functions and deriving them.
chain rule
The Chain Rule is an essential tool in calculus for differentiating composite functions. It allows you to differentiate a function that is nested within another function. Formally, if you have a composite function \( y = f(u) \) and \( u = g(x) \), then the derivative \( \frac{dy}{dx} \) is found as \( \frac{dy}{du} \/ \frac{du}{dx} \).

In our exercise, we need to differentiate \( (f \circ f)(x) \), which involves finding \( f(f(x)) \). The Chain Rule simplifies this by allowing us to handle the nested function \( f(x^2 + 1) \). By applying the Chain Rule methodically, you can differentiate complex compositions by breaking them down into simpler derivatives.
derivative computation
Derivative computation involves finding the rate at which a function changes. In our case, we are using the power rule for differentiation after simplifying the composed function. The power rule states that for any function \( x^n \), the derivative is \( nx^{n-1} \).

After computing \( f(f(x)) \) as \( x^4 + 2x^2 + 2 \), we apply the power rule to each term. For \( x^4 \), its derivative is \( 4x^3 \). For \( 2x^2 \), its derivative is \( 4x \). Constants like \2 \ are zero since their rate of change is constant. Combining these gives us \( 4x^3 + 4x \). This process applies rules mechanically to each term in the function.
calculus
Calculus is a branch of mathematics focused on limits, functions, derivatives, integrals, and infinite series. In this exercise, we are leveraging differential calculus, which is all about understanding how functions change.

By using derivatives, we can analyze the rate of change and the behavior of iterated functions. Calculus tools like the Chain Rule simplify differentiation of complex functions and help in solving real-world problems, from physics to finance.

Mastery of calculus concepts requires practice; working through exercises like this builds a strong foundation for understanding not just how functions interact, but also how they can be utilized in practical scenarios.

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Most popular questions from this chapter

Is the function given by \(f(x)=3 x-2\) continuous at \(x=5 ?\) Why or why not?

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The function \(p(t)=\frac{2000 t}{4 t+75}\) models the population \(p\) of deer in an area after \(t\) months. a) Find \(p^{\prime}(10), p^{\prime}(50),\) and \(p^{\prime}(100)\) b) Find \(p^{\prime \prime}(10), p^{\prime \prime}(50),\) and \(p^{\prime \prime}(100)\) c) Interpret the meaning of your answers to parts (a) and (b). What is happening to this population of deer in the long term?

The population of a city grows from an initial size of 100,000 to a size \(P\) given by \(P(t)=100,000+2000 t^{2}\) where \(t\) is in years. a) Find the growth rate, \(d P / d t\) b) Find the population after 10 yr. c) Find the growth rate at \(t=10\) d) Explain the meaning of your answer to part (c).

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