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Implicit differentiation Use implicit differentiation to find \(\frac{d y}{d x}\). $$y=\frac{x+1}{y-1}$$

Short Answer

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Question: Find the derivative of \(y\) with respect to \(x\) for the function \(y=\frac{x+1}{y-1}\). Answer: \(\frac{dy}{dx}=\frac{1}{2y-1}\)

Step by step solution

01

Rewrite the equation in a more suitable form for differentiation

Multiply both sides of the equation by \((y - 1)\) to get rid of the fraction: $$y(y - 1) = x + 1$$
02

Differentiate both sides with respect to x

Differentiate both sides with respect to x using the product rule and the chain rule on the left side: $$\frac{d}{dx}(y(y-1))=\frac{d}{dx}(x+1)$$
03

Apply product rule and chain rule

Apply the product rule to the left side: \((u*v)' = u'*v + u*v'\) For \(u = y\), \(u' = \frac{d}{dx}(y)\), which we can write as \(\frac{dy}{dx}\). For \(v = (y - 1)\), \(v' = \frac{d}{dx}(y - 1)\) So, we have: $$(y'\cdot(y-1)+y\cdot(y-1)') = 1$$
04

Simplify and solve for \(\frac{dy}{dx}\)

Simplify the equation and isolate \(y'\) (or \(\frac{dy}{dx}\)): $$\frac{dy}{dx}(y-1)+y\frac{d(y-1)}{dx}=1$$
05

Differentiate left side of the equation

We have \(\frac{d(y-1)}{dx} =\frac{dy}{dx}-0\), so the equation becomes: $$\frac{dy}{dx}(y-1)+y\frac{dy}{dx}=1$$ $$\Rightarrow (\frac{dy}{dx})(y-1+y)=1$$ $$\Rightarrow (\frac{dy}{dx})(2y-1)=1$$
06

Solve for \(\frac{dy}{dx}\)

Divide both sides by \((2y - 1)\): $$\frac{dy}{dx}=\frac{1}{2y-1}$$ Thus, the derivative of \(y\) with respect to \(x\) is: $$\frac{dy}{dx}=\frac{1}{2y-1}$$

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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 used for finding derivatives, particularly when dealing with composite functions. Imagine you have a function inside another function, like nesting dolls. The chain rule helps you take the derivative of the outer function and multiply it by the derivative of the inner function. This is essential when working with implicit differentiation, as it often involves layers of functions.In this exercise, when differentiating the term \(y(y - 1)\), the chain rule comes into play. Here's a simple breakdown:
  • Differentiating the inner function: Here, the inner function is \(y - 1\). Derivative of \(y\) with respect to \(x\) is \(\frac{dy}{dx}\), and a constant like \(-1\) becomes zero.
  • Differentiating the outer function: The outer function is \(y(...\). Differentiating \(y\), we still apply \(\frac{dy}{dx}\).
By linking these derivatives, \(\frac{d}{dx}(y(y-1))\) involves using the product and chain rules together, demonstrating the power and necessity of the chain rule in calculus.
Product Rule
The product rule is an integral part of calculus, allowing you to find the derivative of a product of two functions. Understanding how to apply this rule is crucial, especially in implicit differentiation where products of functions often appear.When you have two functions, \(u\) and \(v\), the product rule states:\((uv)' = u'v + uv'\).This means you differentiate the first function, \(u\), multiply it by \(v\), and then add it to the first function, \(u\), multiplied by the derivative of the second function, \(v\).In the exercise example, applying the product rule to \(y(y - 1)\), where:
  • \(u = y, \quad u' = \frac{dy}{dx}\)
  • \(v = (y - 1), \quad v' = \frac{d}{dx}(y-1) = \frac{dy}{dx}\)
The combination of these steps results in the product rule equation:\(y'\cdot(y-1) + y\cdot(y-1)'\).This technique helps manage the complexity of differentiating products of variables, particularly when those variables are implicitly defined.
Derivative
The derivative is a core concept in calculus and represents the rate of change of a function. It's like taking a snapshot of how a function behaves at any given point. When we talk about \(\frac{dy}{dx}\), we are discussing how \(y\) changes as \(x\) changes, which is what derivatives excel at indicating.In implicit differentiation, you're often finding derivatives for equations where \(y\) is tangled with \(x\) in a way that makes direct solutions tricky. Here’s why it's crucial:
  • Error Management: Implicit equations require careful handling since each variable affects the other.
  • Solution Simplification: Simplifying to find \(\frac{dy}{dx}\) allows us to see the relationship between the variables clearly.
In this particular exercise, through implicit differentiation steps, we end up isolating \(\frac{dy}{dx}\). This process usually involves cancelling terms and rearranging the equation, as seen by moving from:\((\frac{dy}{dx})(2y-1) = 1\)to:\(\frac{dy}{dx} = \frac{1}{2y-1}\).Learning to calculate derivatives this way is invaluable for handling complex relationships subtly embedded in mathematical problems.

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Most popular questions from this chapter

Calculate the following derivatives using the Product Rule. $$\begin{array}{lll} \text { a. } \frac{d}{d x}\left(\sin ^{2} x\right) & \text { b. } \frac{d}{d x}\left(\sin ^{3} x\right) & \text { c. } \frac{d}{d x}\left(\sin ^{4} x\right) \end{array}$$ d. Based upon your answers to parts (a)-(c), make a conjecture about \(\frac{d}{d x}\left(\sin ^{n} x\right),\) where \(n\) is a positive integer. Then prove the result by induction.

Given the function \(f,\) find the slope of the line tangent to the graph of \(f^{-1}\) at the specified point on the graph of \(f^{-1}\) . $$f(x)=(x+2)^{2} ;(36,4)$$

One of the Leibniz Rules One of several Leibniz Rules in calculus deals with higher-order derivatives of products. Let \((f g)^{(n)}\) denote the \(n\) th derivative of the product \(f g,\) for \(n \geq 1\) a. Prove that \((f g)^{(2)}=f^{\prime \prime} g+2 f^{\prime} g^{\prime}+f g^{\prime \prime}\) b. Prove that, in general,$$(f g)^{(n)}=\sum_{k=0}^{n}\left(\begin{array}{l} n \\\k\end{array}\right) f^{(k)} g^{(n-k)}$$ where \(\left(\begin{array}{l}n \\\ k\end{array}\right)=\frac{n !}{k !(n-k) !}\) are the binomial coefficients. c. Compare the result of (b) to the expansion of \((a+b)^{n}\).

Derivatives and inverse functions Suppose the slope of the curve \(y=f^{-1}(x)\) at (4,7) is \(\frac{4}{5}\) Find \(f^{\prime}(7)\)

Orthogonal trajectories Two curves are orthogonal to each other if their tangent lines are perpendicular at each point of intersection (recall that two lines are perpendicular to each other if their slopes are negative reciprocals. . A family of curves forms orthogonal trajectories with another family of curves if each curve in one family is orthogonal to each curve in the other family. For example, the parabolas \(y=c x^{2}\) form orthogonal trajectories with the family of ellipses \(x^{2}+2 y^{2}=k,\) where \(c\) and \(k\) are constants (see figure). Use implicit differentiation if needed to find \(d y / d x\) for each equation of the following pairs. Use the derivatives to explain why the families of curves form orthogonal trajectories. \(y=c x^{2} ; x^{2}+2 y^{2}=k,\) where \(c\) and \(k\) are constants

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