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Let \(g(x)=\frac{x}{2 x+5}\). Using the limit de nition of derivative, nd \(g^{\prime}(x)\).

Short Answer

Expert verified
The derivative of \(g(x)=\frac{x}{2 x+5}\) is \(g'(x)=0\).

Step by step solution

01

Substitute into the definition

Start by substituting \(g(x)\) into the limit definition: \(g'(x) = \lim_{h \to 0} \frac{g(x+h) - g(x)}{h}\). So, we have to evaluate \(g(x+h)\) and \(g(x)\) from the function \(g(x)=\frac{x}{2 x+5}\).
02

Evaluate \(g(x+h)\) and \(g(x)\)

To find \(g(x+h)\), replace \(x\) in the function with \(x+h\), which gives \(\frac{x+h}{2(x+h)+5}\). Similarly, \(g(x)\) is \(\frac{x}{2x+5}\). Now substitute both into the limit
03

Simplify the expressions

Substitute \(g(x+h)\) and \(g(x)\) into the limit and simplify. We have \(g'(x)= \lim_{h \to 0} \frac{(\frac{x+h}{2(x+h)+5}) - (\frac{x}{2x+5})}{h}\). Simplify the complex fraction to \(g'(x)= \lim_{h \to 0} \frac{h(2x+5)-(2x+5)(x+h)}{h(4x+10+h)}\). By cancelling out \(h\) from numerator and denominator, we get \(g'(x)= \lim_{h \to 0} \frac{(2x+5)-(2x+5)}{4x+10+h}\). Further solve the limit.
04

Solve the limit

Now we need to evaluate the limit as \(h\) approaches zero. Substitute \(h=0\) into the formula to get \(g'(x)= \frac{0}{4x+10}\). After simplifying the expression, we get \(g'(x)=0\)

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Derivative Calculus
The cornerstone of calculus, the derivative measures how a function changes as its input changes. It's akin to determining the rate of change or the slope of a function at any given point. Using the limit definition, we say that the derivative of a function at a point x, denoted as \(g'(x)\), is the limit of the difference quotient as the increment approaches zero: \[ g'(x) = \lim_{{h \to 0}} \frac{{g(x+h) - g(x)}}{{h}} \]This formula encapsulates how tiny changes in x, represented by h, affect the function's output. The provided exercise uses this definition to find the derivative of a rational function. By evaluating this limit, we gain insight into the instantaneous rate of change of \(g(x)\) at any point x.
Simplifying Complex Fractions
Simplifying complex fractions is critical in calculus, particularly when handling derivatives via the limit definition. A complex fraction involves a fraction in the numerator, the denominator, or both. Simplifying such fractions requires careful manipulation of both the numerator and the denominator to ultimately ensure the terms are in a form that facilitates further mathematical operations.In our exercise, simplification of the complex fraction involves combining \(g(x+h)\) and \(g(x)\) into a single fraction, multiplying out, and finally, eliminating terms with the factor h in both the numerator and the denominator. This step is essential to avoid undefined expressions and to reach a form where the limit as h approaches zero can be evaluated.
Evaluating Limits
Evaluating limits is a fundamental process in calculus used to find the value that a function approaches as the input approaches a certain value. This concept is pivotal when calculating derivatives, because we are interested in the behavior of the function as our change in x, denoted as h, becomes infinitesimally small.In the exercise, we reach the stage where we need to evaluate \( \lim_{{h \to 0}} \) by substituting the value of zero for h. This step is straightforward when our expression is well-simplified, as no indeterminate forms such as \(\frac{0}{0}\) exist. The process requires careful algebraic manipulation to resolve into a determinate form from which we can deduce the limit, and thus, the derivative of the function.
Differentiation of Functions
Differentiation is the action of computing a derivative. The derivative describes the way a function changes at any point and allows us to understand dynamics such as velocity, acceleration, and growth rates in various fields. Differentiation can be approached in several ways, including the limit definition as practiced in our exercise, or through rules such as the power rule, product rule, quotient rule, and chain rule for more complex functions.In the context of the exercise, differentiation of the function \(g(x)\) using the limit definition provides a thorough understanding of the fundamental theorem of calculus, and an appreciation for the delicate process through which we ascertain the behavior of functions. Through the differentiation process, we conclude that the rate of change of \(g(x)\) with respect to x is zero, symbolizing a horizontal tangent line or a constant function.

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Most popular questions from this chapter

Let \(f(x)=\frac{3}{x-5}\). (a) Using the limit de nition of derivative, nd \(f^{\prime}(2)\). (b) Find two ways of checking whether or not your answer is reasonable. These methods should not involve simply checking your algebra. They can be numerical or graphical use your ingenuity.

For Problems 21 through 24 use the limit definition of \(f^{\prime}(a)\) to find the derivative of \(f\) at the point indicated. $$ f(x)=x(x+3) \text { at } x=2 $$

For Problems 21 through 24 use the limit definition of \(f^{\prime}(a)\) to find the derivative of \(f\) at the point indicated. $$ f(x)=(x-3)^{2} \text { at } x=3 $$

Use the limit de nition of derivative to nd the derivative of \(f(x)=k x^{2}\).

You have formed a study group with a few of your friends. One of the people in your study group has been ill for the past \(2 \frac{1}{2}\) weeks and is concerned about the upcoming examination. She needs to understand the main ideas of the past few weeks. Your essay should be designed to help her. (a) Explain the relationship between average rate of change and instantaneous rate of change, and between secant lines and tangent lines. Your classmate is unclear why the definition of derivative involves some limit with \(h\) going to zero. She wants to know why you can't just set \(h=0\) to begin with and be done with it. Why does calculus involve this limit business? (b) She also has one specific question. She is not clear about how you get the graph of \(f^{\prime}\) from the graph of \(f\). Just before she got sick we were doing that. She believes that if the graph of \(f^{\prime}\) is increasing, then the graph of \(f\) is also increasing. Her Course Assistant says this is wrong, but she claims that sometimes she gets the right answer using this reasoning. What's the story? How to write this essay: First, think about your friend's position. Particularly in part (a) see if you can understand what is confusing her and how to clarify it for her. Outline your answer. Then write your essay. Use words precisely. Try to avoid pronouns. For example, do not say "it" is increasing; be specific \(-\) what is increasing? Use words to say precisely what you mean. The real purpose of this essay: These are issues that are important for you to understand. We want you to put together what you have learned in your own words. We also want you to learn to write about mathematics by using words precisely to say exactly what you mean.

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