Chapter 4: Problem 73
Find the differential and evaluate for the given \(x\) and \(d x\). \(y=\frac{1}{x+1}, \quad x=1, \quad d x=0.25\)
Short Answer
Expert verified
The differential \( dy \) is \(-0.0625\).
Step by step solution
01
Find the Derivative
To find the differential, we first need to find the derivative of the function. The given function is \( y = \frac{1}{x+1} \). Let's find \( \frac{dy}{dx} \). Using the quotient rule, where \( u = 1 \) and \( v = x+1 \), the derivative is:\[ \frac{dy}{dx} = \frac{v \cdot \frac{du}{dx} - u \cdot \frac{dv}{dx}}{v^2} = \frac{(x+1) \cdot 0 - 1 \cdot 1}{(x+1)^2} = -\frac{1}{(x+1)^2} \]
02
Express the Differential
The differential \( dy \) is given by \( dy = \frac{dy}{dx} \cdot dx \). From Step 1, we found \( \frac{dy}{dx} = -\frac{1}{(x+1)^2} \). Therefore, the differential is:\[ dy = -\frac{1}{(x+1)^2} \cdot dx \]
03
Evaluate the Differential at Given Values
Plug in the given values of \( x = 1 \) and \( dx = 0.25 \) into the expression for the differential:\[ dy = -\frac{1}{(1+1)^2} \cdot 0.25 = -\frac{1}{4} \cdot 0.25 \]
04
Simplify to Find the Value of the Differential
Calculate the numerical value:\[ dy = -\frac{1}{4} \cdot 0.25 = -0.0625 \]
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Quotient Rule
The quotient rule is a method used in differential calculus to find the derivative of a quotient of two functions.It is especially useful when dealing with rational functions where one function is divided by another.
In general, the quotient rule states that if you have a function \( y = \frac{u(x)}{v(x)} \), the derivative \( \frac{dy}{dx} \) is given by:
In general, the quotient rule states that if you have a function \( y = \frac{u(x)}{v(x)} \), the derivative \( \frac{dy}{dx} \) is given by:
- Find \( \frac{du}{dx} \) and \( \frac{dv}{dx} \), the derivatives of the top and bottom functions respectively.
- Apply the formula \[ \frac{dy}{dx} = \frac{v(x) \cdot \frac{du}{dx} - u(x) \cdot \frac{dv}{dx}}{(v(x))^2} \] to find the derivative of the quotient.
Derivative
A derivative represents the rate of change of a function with respect to a variable.It is a fundamental concept in calculus used to determine the sensitivity of one quantity to a change in another.
When you compute a derivative such as \( \frac{dy}{dx} \), you are essentially finding how much the output \(y\) changes with respect to the input \(x\).
When you compute a derivative such as \( \frac{dy}{dx} \), you are essentially finding how much the output \(y\) changes with respect to the input \(x\).
- For instance, in our example, \( y = \frac{1}{x+1} \), the derivative \[ \frac{dy}{dx} = -\frac{1}{(x+1)^2}\] was calculated using the quotient rule.
- This expression tells us that as \(x\) changes, \(y\) decreases at a rate of \(-\frac{1}{(x+1)^2}\), which indicates an overall decay in the function value as \(x\) increases.
Differential
A differential is a small change in a function resulting from a small change in the input.It is closely linked to derivatives as it uses them to approximate changes in function values.
In simple terms, if you know the derivative of a function, you can use the differential to predict how the function will change for a tiny alteration in \(x\).
In simple terms, if you know the derivative of a function, you can use the differential to predict how the function will change for a tiny alteration in \(x\).
- For our function \( y = \frac{1}{x+1} \), the differential \( dy = -\frac{1}{(x+1)^2} \cdot dx \) reflects how small changes in \(x\) result in changes in \(y\).
- Given \( x=1 \) and \( dx = 0.25 \), the differential evaluates to \( dy = -0.0625 \), meaning the function \(y\) decreases by about 0.0625 when \(x\) increases by 0.25.