Chapter 3: Problem 56
For the following exercises, use the definition of a derivative to find \(f^{\prime}(x)\) . $$f(x)=\frac{2 x}{7}+1$$
Short Answer
Expert verified
The derivative \( f'(x) = \frac{2}{7} \).
Step by step solution
01
Understand the Definition of a Derivative
The definition of the derivative of a function \( f(x) \) at a point \( x \) is given by the limit \[ f'(x) = \lim_{h \to 0} \frac{f(x+h) - f(x)}{h} \]. Our task is to apply this definition to find \( f'(x) \) for the function \( f(x) = \frac{2x}{7} + 1 \).
02
Substitute into the Derivative Definition
Substitute \( f(x) = \frac{2x}{7} + 1 \) and \( f(x+h) = \frac{2(x+h)}{7} + 1 \) into the derivative formula. The subtraction \( f(x+h) - f(x) \) becomes: \[ \frac{2(x+h)}{7} + 1 - \left(\frac{2x}{7} + 1\right) \].
03
Simplify the Expression
Simplify \( \frac{2(x+h)}{7} + 1 - \left(\frac{2x}{7} + 1\right) \). The 1s will cancel out, and the expression simplifies to: \[ \frac{2x + 2h}{7} - \frac{2x}{7} = \frac{2h}{7} \].
04
Calculate the Limit
Now, calculate the limit: \( \lim_{h \to 0} \frac{\frac{2h}{7}}{h} \). This simplifies to \( \lim_{h \to 0} \frac{2}{7} \), which is just \( \frac{2}{7} \) since it does not depend on \( h \).
05
State the Derivative
After evaluating the limit, we find that \( f'(x) = \frac{2}{7} \). This means that the derivative of the function \( f(x) = \frac{2x}{7} + 1 \) is a constant, \( \frac{2}{7} \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Definition of Derivative
The derivative of a function is a fundamental concept in calculus. It essentially tells us how a function changes as its input changes. To find the derivative of a function, we use the definition:
- The derivative of a function \( f(x) \) at a point \( x \) is expressed as: \[ f'(x) = \lim_{h \to 0} \frac{f(x+h) - f(x)}{h} \] This formula is crucial for calculating the rate of change of the function at any given point.
- In our example, we apply this definition to the function \( f(x) = \frac{2x}{7} + 1 \).
Limit Process
The limit process is an essential step in finding a derivative. It's the step where we see how the function behaves as its inputs change infinitesimally.
- For our function \( f(x) = \frac{2x}{7} + 1 \), we substitute the expressions \( f(x) \) and \( f(x+h) \) into the derivative formula.
- The subtraction \( f(x+h) - f(x) \) is simplified to \( \frac{2(x+h)}{7} + 1 - \left(\frac{2x}{7} + 1\right) \).
Function Simplification
Function simplification is often necessary while working with derivatives to make calculations easier. This involves algebraically reducing complex expressions to simpler forms.
- In this exercise, after substituting the expressions into the derivative formula, simplifying \( \frac{2(x+h)}{7} + 1 - \left(\frac{2x}{7} + 1\right) \) results in \( \frac{2h}{7} \).
- This involves cancelling out the constant terms and terms involving \( x \).
Constant Derivative
When calculating derivatives, sometimes you find a special case where the derivative is a constant value. This means that the rate of change of the function is uniform regardless of \( x \).
- For the function \( f(x) = \frac{2x}{7} + 1 \), after completing the limit process, we found that \( f'(x) \) is \( \frac{2}{7} \).
- This indicates a constant derivative, representing a straight-line slope for the linear function given.