Chapter 14: Problem 5
Find the partial derivatives. The variables are restricted to a domain on which the function is defined. $$\frac{\partial z}{\partial x} \text { and } \frac{\partial z}{\partial y} \text { if } z=\left(x^{2}+x-y\right)^{7}$$
Short Answer
Expert verified
\( \frac{\partial z}{\partial x} = 7(2x + 1)(x^2 + x - y)^6 \) and \( \frac{\partial z}{\partial y} = -7(x^2 + x - y)^6 \).
Step by step solution
01
Understand the Problem
We need to find the partial derivatives \( \frac{\partial z}{\partial x} \) and \( \frac{\partial z}{\partial y} \) of the function \( z = (x^2 + x - y)^7 \). A partial derivative measures how a function changes as only one of the independent variables change while the other variables are held constant.
02
Apply the Chain Rule for \( \frac{\partial z}{\partial x} \)
To find \( \frac{\partial z}{\partial x} \), apply the chain rule. Let \( u = x^2 + x - y \), so we have \( z = u^7 \).1. Find \( \frac{\partial z}{\partial u} = 7u^6 \).2. Then find \( \frac{\partial u}{\partial x} = 2x + 1 \). 3. Use the chain rule: \( \frac{\partial z}{\partial x} = \frac{\partial z}{\partial u} \cdot \frac{\partial u}{\partial x} = 7(x^2 + x - y)^6 \cdot (2x + 1) \).
03
Simplify \( \frac{\partial z}{\partial x} \)
Simplify the expression obtained: \[ \frac{\partial z}{\partial x} = 7(2x + 1)(x^2 + x - y)^6 \].
04
Apply the Chain Rule for \( \frac{\partial z}{\partial y} \)
Next, find \( \frac{\partial z}{\partial y} \) using a similar process. 1. We already have \( \frac{\partial z}{\partial u} = 7u^6 \).2. Find \( \frac{\partial u}{\partial y} = -1 \) since \( u = x^2 + x - y \).3. Use the chain rule: \( \frac{\partial z}{\partial y} = \frac{\partial z}{\partial u} \cdot \frac{\partial u}{\partial y} = 7(x^2 + x - y)^6 \cdot (-1) \).
05
Simplify \( \frac{\partial z}{\partial y} \)
Simplify the expression obtained: \[ \frac{\partial z}{\partial y} = -7(x^2 + x - y)^6 \].
06
Conclusion
The partial derivatives are:1. \( \frac{\partial z}{\partial x} = 7(2x + 1)(x^2 + x - y)^6 \).2. \( \frac{\partial z}{\partial y} = -7(x^2 + x - y)^6 \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Chain Rule
When dealing with functions of multiple variables, like our exercise function \( z = (x^2 + x - y)^7 \), the chain rule helps simplify the differentiation process. The chain rule is used when a variable, say \( z \), is a function of another variable, \( u \), which is itself a function of yet another variable. This is perfect when we have composite functions.
In the case of finding \( \frac{\partial z}{\partial x} \), we first set \( u = x^2 + x - y \), turning our function into \( z = u^7 \).
In the case of finding \( \frac{\partial z}{\partial x} \), we first set \( u = x^2 + x - y \), turning our function into \( z = u^7 \).
- First, find \( \frac{\partial z}{\partial u} \) by differentiating \( z = u^7 \) with respect to \( u \), resulting in \( 7u^6 \).
- Next, find \( \frac{\partial u}{\partial x} \) by differentiating \( x^2 + x - y \) with respect to \( x \), giving \( 2x + 1 \).
- Finally, apply the product of these derivatives to find \( \frac{\partial z}{\partial x} = 7(x^2 + x - y)^6(2x + 1) \).
Multivariable Calculus
Multivariable calculus involves dealing with functions that depend on more than one variable. Unlike single-variable calculus where functions depend on one variable, multivariable calculus expands this idea, helping us describe a vast range of real-world situations like physics and engineering problems.
In our exercise, \( z = (x^2 + x - y)^7 \) involves three variables \( x \), \( y \), and \( z \). To analyze how \( z \) changes, we need to determine the partial derivatives \( \frac{\partial z}{\partial x} \) and \( \frac{\partial z}{\partial y} \).
In our exercise, \( z = (x^2 + x - y)^7 \) involves three variables \( x \), \( y \), and \( z \). To analyze how \( z \) changes, we need to determine the partial derivatives \( \frac{\partial z}{\partial x} \) and \( \frac{\partial z}{\partial y} \).
- Partial derivatives provide us a way to observe how a small change in one variable affects the overall function while holding other variables constant.
- This approach helps in understanding the behavior of complex systems modeled by multivariable functions.
- It offers insights into how different components of a system influence each other.
Function Differentiation
Differentiation of functions, especially in calculus, is the process of finding the derivative, which is a measure of how a function changes as its input changes.
For our given function, \( z = (x^2 + x - y)^7 \), differentiation helps in understanding how the output \( z \) reacts to changes in \( x \) or \( y \).
For our given function, \( z = (x^2 + x - y)^7 \), differentiation helps in understanding how the output \( z \) reacts to changes in \( x \) or \( y \).
- The process involves using rules and formulas, like the chain rule, to simplify and calculate derivatives efficiently.
- By finding \( \frac{\partial z}{\partial x} \), it indicates how \( z \) changes with a small change in \( x \).
- Similarly, \( \frac{\partial z}{\partial y} \) shows how \( z \) alters with a small change in \( y \).
- These partial derivatives give the rates of change in the direction of each variable separately.