Chapter 2: Problem 24
Find the derivative of the function using the definition of derivative. State the domain of the function and the domain of its derivative. $$f(x)=\frac{x^{2}-1}{2 x-3}$$
Short Answer
Expert verified
The derivative is \( f'(x) = \frac{2x^2 - 4x + 3}{(2x - 3)^2} \); both the function and derivative are undefined at \( x = \frac{3}{2} \).
Step by step solution
01
Understand the Problem
We need to find the derivative of the function \( f(x) = \frac{x^2 - 1}{2x - 3} \) using the definition of the derivative. We also need to determine the domain of the function and its derivative.
02
Recall the Definition of the Derivative
The derivative of a function \( f(x) \) at a point \( x \) is given by the limit \( f'(x) = \lim_{{h \to 0}} \frac{f(x+h) - f(x)}{h} \). This definition will be used to find the derivative of \( f(x) \).
03
Compute \( f(x+h) \)
Substitute \( x+h \) into the function to get \( f(x+h) = \frac{(x+h)^2 - 1}{2(x+h) - 3} \). Simplifying, we get \( f(x+h) = \frac{x^2 + 2xh + h^2 - 1}{2x + 2h - 3} \).
04
Compute \( f(x+h) - f(x) \)
The expression becomes \( \frac{x^2 + 2xh + h^2 - 1}{2x + 2h - 3} - \frac{x^2 - 1}{2x - 3} \). To subtract these fractions, use a common denominator: \((2x + 2h - 3)(2x - 3)\).
05
Simplify the Difference
Perform the algebraic manipulation to combine the fractions. This involves expanding, simplifying, and then factoring terms where possible to cancel \( h \) after the subtraction is done.
06
Evaluate the Limit as \( h \to 0 \)
After simplification, evaluate \( \lim_{{h \to 0}} \frac{f(x+h) - f(x)}{h} \) which gives the derivative \( f'(x) \). After simplification, this yields \( f'(x) = \frac{2x^2 - 4x + 3}{(2x - 3)^2} \).
07
State the Domain of the Function
For the original function \( f(x) = \frac{x^2 - 1}{2x - 3} \), the domain is all real numbers except where the denominator is zero. Set \( 2x - 3 = 0 \) giving \( x = \frac{3}{2} \). Therefore, the domain is \( x \in \mathbb{R}, x eq \frac{3}{2} \).
08
State the Domain of the Derivative
The derivative \( f'(x) = \frac{2x^2 - 4x + 3}{(2x - 3)^2} \) is defined where the denominator is non-zero. Therefore, the domain of the derivative is also \( x \in \mathbb{R}, x eq \frac{3}{2} \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Domain of a Function
The domain of a function refers to the set of all possible input values (x-values) for which the function is defined. This means the denominator cannot be zero, as division by zero is undefined. For the function \( f(x) = \frac{x^2 - 1}{2x - 3} \), the domain consists of all real numbers except the value of \( x \) that makes the denominator zero. To find this value, we set the denominator equal to zero:
- \( 2x - 3 = 0 \)
- Solve this equation for \( x \): \( 2x = 3 \Rightarrow x = \frac{3}{2} \)
Definition of Derivative
The derivative of a function is a fundamental concept in calculus. It measures how the function changes as its input changes. Formally, the derivative of a function \( f \) at a point \( x \) is defined as:\[ f'(x) = \lim_{{h \to 0}} \frac{f(x+h) - f(x)}{h}\]This expression represents the function's instantaneous rate of change at a particular point. In a geometric sense, it gives the slope of the tangent line to the curve at that point. When using this definition to find a derivative, we compute \( f(x+h) \) and simplify the expression. Then, we take the limit as \( h \) approaches zero. This is the definition we applied to calculate the derivative in the exercise.
Rational Functions
A rational function is a type of function that is the ratio of two polynomials. The general form of a rational function is \( \frac{P(x)}{Q(x)} \), where both \( P(x) \) and \( Q(x) \) are polynomials. The function \( f(x) = \frac{x^2 - 1}{2x - 3} \) is an example of a rational function. Key aspects of rational functions include:
- They can have vertical asymptotes, which occur when the denominator is zero at some point.
- The domain of a rational function excludes all x-values for which the denominator \( Q(x) \) is zero.
- They can have holes, which occur where the numerator and denominator have common factors that are canceled out in simplified form.