Chapter 4: Problem 28
Calculate the linear approximation for \(f(x)\) : $$f(x) \approx f(a)+f^{\prime}(a)(x-a)$$ \(f(x)=(1-x)^{-n}\) at \(a=0 .\) (Assume that \(n\) is a positive integer.)
Short Answer
Expert verified
The linear approximation is \( f(x) \approx 1 + nx \).
Step by step solution
01
Identify the Function Components
First, notice that the function we are working with is \( f(x) = (1-x)^{-n} \). We need to identify the function and its derivative at the point \( a = 0 \) for the linear approximation formula.
02
Evaluate the Function at a
Next, calculate \( f(a) \), where \( a = 0 \). This is simply \( f(0) = (1-0)^{-n} = 1 \).
03
Find the Derivative of the Function
The derivative of \( f(x) = (1-x)^{-n} \) is found using the chain rule. The derivative is \( f'(x) = n(1-x)^{-n-1} \).
04
Evaluate the Derivative at a
Calculate \( f'(a) \) where \( a = 0 \). Substituting in, we find \( f'(0) = n(1-0)^{-n-1} = n \).
05
Substitute into the Linear Approximation Formula
Replace \( f(a) \) and \( f'(a) \) into the linear approximation formula: \[ f(x) \approx f(0) + f'(0)(x-0) = 1 + n \cdot (x - 0) = 1 + nx \].
06
Write the Final Linear Approximation
The linear approximation of \( f(x) = (1-x)^{-n} \) at \( a = 0 \) is \( f(x) \approx 1 + nx \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Understanding Calculus
Calculus is a branch of mathematics that deals with change. It provides tools to find how things change, accumulate, grow, or shrink. Central to calculus are two fundamental ideas: differentiation and integration. These concepts allow us to:
- Understand rates of change, such as velocity and acceleration.
- Calculate areas under curves and volumes of objects.
Delving into Derivatives
Derivatives represent how a function changes as the input changes, calculated as the "slope" of the function at any given point. Imagine a car driving on a curvy road. At any instant, the speedometer tells you how fast the car is going, which is akin to finding the derivative. For the function \( f(x) = (1-x)^{-n} \), the derivative helps us understand how rapidly it changes as \( x \) shifts.
- Finding the derivative of a function involves applying rules and formulas of differentiation.
- A critical utility of derivatives is in linear approximation — determining how a function's change can be approximated linearly at a point.
Exploring the Chain Rule in Differentiation
The chain rule is an essential tool in calculus for finding derivatives of composed functions. It states that to differentiate a composite function, you multiply the derivative of the outer function by the derivative of the inner function. For a function like \( (1-x)^{-n} \), which is a composition of a basic power function and a linear function, the chain rule becomes quite handy.
- First, identify the outer function \( y = (1-x)^{-n} \) and the inner function \( u = 1-x \).
- The derivative of the outer function with respect to the inner is \( -n(1-x)^{-n-1} \), while the derivative of the inner function \( 1-x \) is \(-1\).