Chapter 2: Problem 4
Find \(d^{3} y / d x^{3}\). $$ y=(3-5 x)^{5} $$
Short Answer
Expert verified
The third derivative is \(-7500(3 - 5x)^2\).
Step by step solution
01
Apply Chain Rule for First Derivative
Start by finding the first derivative, \(\frac{dy}{dx}\), of the function \(y = (3 - 5x)^5\). Set \(u = 3 - 5x\), then \(y = u^5\). Using the chain rule, \(\frac{dy}{dx} = \frac{dy}{du} \cdot \frac{du}{dx}\). First, compute \(\frac{dy}{du} = 5u^4\) and \(\frac{du}{dx} = -5\). Therefore, \(\frac{dy}{dx} = 5u^4 \cdot (-5) = -25(3 - 5x)^4\).
02
Differentiate to Find Second Derivative
Next, differentiate \(\frac{dy}{dx} = -25(3 - 5x)^4\) to find \(\frac{d^2y}{dx^2}\). Again, use the chain rule: let \(v = (3 - 5x)\), then differentiate \(-25v^4\). The derivative is \(-25 \cdot 4v^3 \cdot \frac{dv}{dx}\). Since \(\frac{dv}{dx} = -5\), we get \(\frac{d^2y}{dx^2} = -25 \cdot 4v^3 \cdot (-5) = 500(3 - 5x)^3\).
03
Find the Third Derivative
Differentiate \(\frac{d^2y}{dx^2} = 500(3 - 5x)^3\) to find \(\frac{d^3y}{dx^3}\). Letting \(w = (3 - 5x)\), differentiate \(500w^3\) to get \(500 \cdot 3w^2 \cdot \frac{dw}{dx}\). Since \(\frac{dw}{dx} = -5\), the result is \(\frac{d^3y}{dx^3} = 500 \cdot 3w^2 \cdot (-5) = -7500(3 - 5x)^2\).
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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 technique in calculus used for finding the derivative of composite functions. When you have a function nested inside another function, the chain rule helps you differentiate it by breaking it down into simpler parts. Typically, it follows this format: if you have a function such as \( y = f(g(x)) \), then the derivative \( \frac{dy}{dx} \) can be obtained by multiplying the derivative of the outer function \( f \) by the derivative of the inner function \( g \).
- Let's consider \( y = (3 - 5x)^5 \) which is a composite function, where \( u = 3 - 5x \) and \( y = u^5 \).
- First, we differentiate the outer function: \( \frac{dy}{du} = 5u^4 \).
- Next, we differentiate the inner function: \( \frac{du}{dx} = -5 \).
- According to the chain rule, \( \frac{dy}{dx} = \frac{dy}{du} \cdot \frac{du}{dx} = 5u^4 \cdot (-5) = -25(3 - 5x)^4 \).
Differentiation
Differentiation is one of the core operations in calculus, allowing us to compute the rate at which one quantity changes with respect to another. When you differentiate a function, you find its derivative. The process involves applying various rules and techniques, such as the power rule, product rule, quotient rule, and chain rule.
- In the given function \( y = (3 - 5x)^5 \), differentiation first requires applying the chain rule to find the first derivative.
- The second derivative involves differentiating \( \frac{dy}{dx} = -25(3-5x)^4 \). Again, using the chain rule, we find \( \frac{d^2y}{dx^2} = 500(3-5x)^3 \).
- Finally, for the third derivative, the process requires differentiating \( \frac{d^2y}{dx^2} = 500(3 - 5x)^3 \) to obtain \( \frac{d^3y}{dx^3} = -7500(3 - 5x)^2 \).
Calculus
Calculus is a branch of mathematics that explores changes and motion. It is primarily divided into two branches: differential calculus and integral calculus. In this exercise, we're dealing with differential calculus, which focuses on finding the derivative of a function.
- The derivative measures how a function changes as its input changes; it is a fundamental concept for understanding and predicting the behavior of functions.
- In real life, derivatives represent various rates: speed is the derivative of position, and acceleration is the derivative of speed. This makes calculus incredibly powerful in physical applications.
- Applying calculus through techniques like the chain rule allows us to handle complex functions, such as \( y = (3 - 5x)^5 \), more easily. By finding its first, second, and third derivatives, we gain insights into how the function behaves at different levels of change.