Chapter 4: Problem 58
Find f such that: $$ f^{\prime}(x)=\frac{2}{\sqrt[3]{x}}, \quad f(1)=1 $$
Short Answer
Expert verified
The function is \( f(x) = 3x^{2/3} - 2 \).
Step by step solution
01
Understand the Problem
We are given the derivative of a function, \( f'(x) = \frac{2}{\sqrt[3]{x}} \), and we need to find the original function, \( f(x) \). Additionally, we have the condition that \( f(1) = 1 \), which will help us find the constant of integration.
02
Find the Antiderivative
To find \( f(x) \), we need to integrate \( f'(x) \). The expression \( \frac{2}{\sqrt[3]{x}} \) can be rewritten as \( 2x^{-1/3} \). The integral becomes: \[\int f'(x) \, dx = \int 2x^{-1/3} \, dx.\] Use the power rule for integrals: \( \int x^n \, dx = \frac{x^{n+1}}{n+1} + C \), applying it here gives us:\[f(x) = 2 \cdot \frac{x^{2/3}}{2/3} + C = 3x^{2/3} + C.\]
03
Use the Initial Condition
We know that \( f(1) = 1 \). Substitute \( x = 1 \) into \( f(x) = 3x^{2/3} + C \):\[1 = 3 \cdot 1^{2/3} + C.\]This simplifies to:\[1 = 3 + C.\]Solving this equation for \( C \) gives \( C = -2 \).
04
Write the Final Function
Substitute \( C = -2 \) back into the expression for \( f(x) \): \[f(x) = 3x^{2/3} - 2.\] This is the function that satisfies both the derivative and the initial condition.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Antiderivative
When tackling a problem involving derivatives like this, our goal is to find the original function from its derivative, known as finding the "antiderivative." The antiderivative is essentially the reverse of taking a derivative, meaning we are trying to find a function whose derivative gives us the function we started with. In integration, this is symbolized by the integral sign \( \int \), and our task is to
- Convert the given derivative expression into a form we can integrate easily.
- Remember that the process results in a function with a constant \( C \), known as the constant of integration.
Power Rule
The power rule for finding antiderivatives is a fundamental tool in calculus. It helps us integrate functions of the form \( x^n \). The rule states that
- \( \int x^n \, dx = \frac{x^{n+1}}{n+1} + C \) when \( n eq -1 \).
Initial Condition
An initial condition helps us find the constant of integration, \( C \), turning our general solution into a specific one. In this problem, the initial condition is given as \( f(1) = 1 \), which provides a specific value of \( x \) that makes it possible to compute \( C \).Here's how to use an initial condition:
- Substitute the values \( x = 1 \) and \( f(x) = 1 \) into the general antiderivative \( f(x) = 3x^{2/3} + C \).
- Solve the equation to isolate and find \( C \):
- \( 1 = 3 \cdot 1^{2/3} + C \).
- \( 1 = 3 + C \).
- \( C = -2 \).