Chapter 4: Problem 30
Suppose that \(f(0)=5\) and that \(f^{\prime}(x)=2\) for all \(x .\) Must \(f(x)=\) \(2 x+5\) for all \(x ?\) Give reasons for your answer.
Short Answer
Expert verified
Yes, because \( f(x) = 2x + 5 \) satisfies both \( f'(x) = 2 \) and \( f(0) = 5 \).
Step by step solution
01
Understanding the Problem
We are given that \( f(0) = 5 \) and \( f'(x) = 2 \) for all \( x \). The task is to determine if \( f(x) \) is equal to \( 2x + 5 \) for all \( x \).
02
Analyze the Derivative of f(x)
Since \( f'(x) = 2 \) is constant for all \( x \), it means that the function \( f(x) \) is linear. Therefore, \( f(x) = 2x + C \), where \( C \) is a constant to be determined.
03
Use the Given Condition f(0) = 5
We know \( f(0) = 5 \). Substitute \( x = 0 \) into the equation \( f(x) = 2x + C \): \[ f(0) = 2(0) + C = C = 5 \]. Thus, \( C = 5 \).
04
Write the Final Function
Substitute \( C = 5 \) back into \( f(x) = 2x + C \). The function becomes \( f(x) = 2x + 5 \).
05
Verify the Conclusion
The derived function \( f(x) = 2x + 5 \) satisfies both \( f'(x) = 2 \) for all \( x \) and \( f(0) = 5 \). Thus, this is the correct function.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Constant function
A constant function is one of the simplest types of functions in mathematics. It is a function where the output value remains the same regardless of the input. In mathematical terms, a constant function is expressed as \( f(x) = c \) where \( c \) is a constant.
This means that no matter what value of \( x \) you plug into a constant function, the output will always be \( c \). It's like having a straight horizontal line on a graph.
This means that no matter what value of \( x \) you plug into a constant function, the output will always be \( c \). It's like having a straight horizontal line on a graph.
- The derivative of a constant function is always zero, which means its rate of change is zero.
- Constant functions are always parallel to the x-axis and never intersect it.
Linear function
Linear functions are a step up in complexity from constant functions. They have the form \( f(x) = mx + b \), where \( m \) is the slope and \( b \) is the y-intercept.
This function represents a straight line on a graph. Unlike a constant function's horizontal line, a linear function can have a slope that makes the line rise or fall.
This function represents a straight line on a graph. Unlike a constant function's horizontal line, a linear function can have a slope that makes the line rise or fall.
- The slope \( m \) indicates the rate of change; a positive \( m \) means the line ascends, while negative \( m \) means it descends.
- The y-intercept \( b \) indicates where the line crosses the y-axis.
Integration
Integration is the mathematical process of finding the integral of a function. It is essentially the reverse operation of differentiation.
When you integrate a function, you are looking for the function with a derivative that matches the original function. For example, the integral of \( 2 \) with respect to \( x \) is \( 2x + C \), where \( C \) is the integration constant.
When you integrate a function, you are looking for the function with a derivative that matches the original function. For example, the integral of \( 2 \) with respect to \( x \) is \( 2x + C \), where \( C \) is the integration constant.
- Integration can be thought of as finding the area under the curve of a graphed function.
- Definite integration results in a numerical area value, while indefinite integration includes the \( C \).
Initial condition
Initial conditions are critical in determining the specific form of a function when solving differential equations.
These conditions provide a specific value for the function at a particular point, allowing us to find the constant of integration. In our exercise, \( f(0) = 5 \) serves as an initial condition, telling us how the line \( f(x) = 2x + C \) should be positioned on the coordinate plane.
These conditions provide a specific value for the function at a particular point, allowing us to find the constant of integration. In our exercise, \( f(0) = 5 \) serves as an initial condition, telling us how the line \( f(x) = 2x + C \) should be positioned on the coordinate plane.
- Substituting the initial condition into the integrated function helps solve for \( C \), ensuring the function matches specified conditions.
- Without an initial condition, there is an infinite number of functions that could satisfy a given differential equation.