Chapter 7: Problem 50
Find \(d x / d y\). $$ y=x-2 / x \text { for } x<0 $$
Short Answer
Expert verified
The derivative \( \frac{dx}{dy} = \frac{1}{1 + \frac{2}{x^2}} \).
Step by step solution
01
Express y in terms of x
Given the equation, rearrange it to explicitly write the expression for \(y\) in terms of \(x\):\[ y = x - \frac{2}{x} \]
02
Differentiate y with respect to x
To find \( \frac{dy}{dx} \), differentiate the expression obtained in step 1 with respect to \(x\): \[ \frac{dy}{dx} = \frac{d}{dx} \left(x - \frac{2}{x}\right). \] Use the derivative rules: the derivative of \(x\) is 1, and the derivative of \(-\frac{2}{x}\) using the power rule is \(\frac{2}{x^2}\). Thus, \[ \frac{dy}{dx} = 1 + \frac{2}{x^2}. \]
03
Find dx/dy
To find \( \frac{dx}{dy} \), we need to find the reciprocal of \( \frac{dy}{dx} \). Hence,\[ \frac{dx}{dy} = \frac{1}{\frac{dy}{dx}} = \frac{1}{1 + \frac{2}{x^2}}. \]
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Understanding Derivatives
Derivatives are a core concept in calculus, representing the rate at which a function changes. In more intuitive terms, if you imagine a curve on a graph, the derivative at a specific point tells you how steep the curve is at that point. This steepness is essentially the slope of the tangent line to the curve.
- The derivative of a function is commonly denoted by \( \frac{dy}{dx} \), representing the change in \( y \) with respect to the change in \( x \).
- To compute derivatives, we use various rules such as the power rule, product rule, and chain rule, depending on the form of the function.
- The result of a derivative function provides insights into increasing or decreasing behavior of the original function, concavity, and inflection points.
Exploring Reciprocal Functions
A reciprocal function is a specific type of function where each output value is the reciprocal (or multiplicative inverse) of the input. Mathematically, if you have a function like \( f(x) = \frac{1}{x} \), it is called a reciprocal function.
- Reciprocal functions lead to interesting behaviors, especially when it comes to differentiation, as it often involves transforming the exponent in the denominator.
- In the context of our exercise, after differentiating \( y \) with respect to \( x \) and obtaining \( \frac{dy}{dx} \), finding the reciprocal gives us \( \frac{dx}{dy} \), which is essentially flipping the derivative to yield a new perspective on the rate of change.
- Understanding reciprocal relationships helps unravel complex expressions in calculus and solve differential equations.
Applying the Power Rule
The power rule is a straightforward yet powerful tool in calculus for differentiating functions of the form \( x^n \). According to the power rule, if \( f(x) = x^n \), then the derivative \( \frac{df}{dx} \) is \( nx^{n-1} \).
- This rule dramatically simplifies the differentiation process, especially when dealing with polynomial functions.
- When applying the power rule to our exercise's function \( y = x - \frac{2}{x} \), remember that \( \frac{2}{x} \) can be rewritten as \( 2x^{-1} \), making differentiation straightforward using the power rule, resulting in \( \frac{2}{x^2} \) for that term.
- The power rule is not just limited to whole numbers but also applies to negative and fractional exponents, broadening its applications across various calculus problems.