Chapter 3: Problem 107
Using the Chain Rule, show that the Power Rule \((d / d x) x^{n}=n x^{n-1}\) holds for the functions \(x^{n}\) in Exercises 107 and 108. $$x^{1 / 4}=\sqrt{\sqrt{x}}$$
Short Answer
Expert verified
The derivative is \( \frac{1}{4}x^{-3/4} \).
Step by step solution
01
Rewrite the Function
First, express the function in terms of a single power of x. For the function given, \( x^{1/4} = (x^{1/2})^{1/2} \) which simplifies to \( x^{1/4} \).
02
Identify the Exponent
Identify the exponent \( n \) in the expression \( x^{n} \). In this case, \( n = \frac{1}{4} \).
03
Apply the Power Rule
According to the Power Rule, \( \frac{d}{dx} x^{n} = n x^{n-1} \). Plugging our specific \( n \) value into this formula yields \( \frac{1}{4} x^{1/4-1} = \frac{1}{4} x^{-3/4} \).
04
Use the Chain Rule Justification
Confirm that no further adjustment is needed using the chain rule. For \((x^{m})^{n}\), the derivative is \(mn(x^{mn-1})\) when using \( n = \frac{1}{2} \) and \( m = \frac{1}{2} \), we have \( (1/2)(1/2)x^{1/4 - 1} = 1/4 x^{-3/4} \), matching the result of applying the Power Rule.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Power Rule
The Power Rule is a fundamental concept in calculus, especially when taking derivatives. This rule provides a straightforward method for finding the derivative of a function that is a power of x. Specifically, if you have a function of the form \(x^n\), where \(n\) is any real number, the derivative is calculated as \(\frac{d}{dx} x^n = n x^{n-1}\).
What makes the Power Rule so handy is its simplicity and applicability to a wide variety of problems. You simply bring down the exponent as a coefficient, and then reduce the exponent by one. This technique is fast and easy, even when the exponent is a fraction or a negative number.
What makes the Power Rule so handy is its simplicity and applicability to a wide variety of problems. You simply bring down the exponent as a coefficient, and then reduce the exponent by one. This technique is fast and easy, even when the exponent is a fraction or a negative number.
- Example: If \(f(x) = x^{3}\), then the derivative \(f'(x) = 3x^{3-1} = 3x^{2}\).
- For \(f(x) = x^{1/4}\), the derivative is \(f'(x) = \frac{1}{4}x^{-3/4}\), by applying the power rule and using fraction manipulation.
Derivative
A derivative measures how a function changes as its input changes. Conceptually, it's the mathematical representation of a function's rate of change at any given point. Think of it like the speedometer in your car; it tells you the speed (or rate of change) at a precise moment.
For our exercise, determining the derivative of \(x^{1/4}\) involved applying the Power Rule effectively, showing how derivatives help us understand the behavior and changes of polynomial functions.
- The derivative of a function \(f(x)\) is usually represented as \(f'(x)\) or \(\frac{d}{dx}f(x)\).
- In the context of calculus, finding a derivative involves applying analytical methods, such as the Power Rule, Chain Rule, or other rules of differentiation.
For our exercise, determining the derivative of \(x^{1/4}\) involved applying the Power Rule effectively, showing how derivatives help us understand the behavior and changes of polynomial functions.
Exponentiation
Exponentiation is a mathematical operation involving two numbers: a base and an exponent. It's a shorthand for expressing repeated multiplication. The base is the number being multiplied, and the exponent indicates how many times the base is used as a factor.
In our exercise, exponentiation played a key role in simplifying the function and applying the Power Rule accurately, as the expression was initially \(\sqrt{\sqrt{x}}\), which we expressed as \((x^{1/2})^{1/2} = x^{1/4}\). Understanding this transformation is vital when dealing with complex polynomial expressions and their derivatives.
- For example, \(x^2\) means \(x\) is multiplied by itself: \(x \times x\).
- When the exponent is a fraction, such as \(x^{1/4}\), it represents the root of the base. Here, \(x^{1/4}\) corresponds to the fourth root of \(x\), or \(\sqrt[4]{x}\).
In our exercise, exponentiation played a key role in simplifying the function and applying the Power Rule accurately, as the expression was initially \(\sqrt{\sqrt{x}}\), which we expressed as \((x^{1/2})^{1/2} = x^{1/4}\). Understanding this transformation is vital when dealing with complex polynomial expressions and their derivatives.