Limit definition for derivation of f(x) HELPtutoring my daughter and I'm stuck

As h--> 0, [f(x+h)- f(x)]/h--> 2x- 4.In summary, the limit definition of the derivative of f(x) = x^2- 4x is 2x- 4.
  • #1
epatjn
1
0

Homework Statement



Here's the question...use the limit defintion to find the derivation of f(x) = x^2-4x

Homework Equations



does this use the defintion of the derivative formula (using Larson, et al 4th edition of Precaclulus graphing with limits...and trying to teach someone what to do, but am at a loss at present on what to do...

The Attempt at a Solution

 
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  • #2


epatjn said:

Homework Statement



Here's the question...use the limit defintion to find the derivation of f(x) = x^2-4x

Homework Equations



does this use the defintion of the derivative formula (using Larson, et al 4th edition of Precaclulus graphing with limits...and trying to teach someone what to do, but am at a loss at present on what to do...

The Attempt at a Solution

I don't have the Larson book, but I assume it defines the derivative (not _derivation_) of f at x to be the limit of the ratio [f(x+h) - f(x)]/h as h --> 0. Well, you can calculate f(x+h) and you know f(x), so you can see what the ratio is equal to. Then you can see what it becomes closer and closer to as h becomes smaller and smaller.

RGV
 
  • #3


f(x)= x^2- 4x so f(x+h)= (x+h)^2- 4(x+h)= x^2+ 2hx+ h^2- 4x- 4h

f(x+h)- f(x)= x^2+ 2hx+ h^2- 4x- 4h- (x^2- 4x)= 2hx+ h^2- 4h
 

Related to Limit definition for derivation of f(x) HELPtutoring my daughter and I'm stuck

1. What is a limit definition for derivation of f(x)?

A limit definition for derivation of f(x) is a mathematical concept that describes the instantaneous rate of change of a function at a specific point. It involves taking the limit of the slope of a secant line as the distance between two points approaches zero.

2. Why is it important to understand limit definition for derivation of f(x)?

Understanding limit definition for derivation of f(x) is important because it is the foundation for understanding the concept of derivatives, which are essential in many areas of mathematics and science. It also helps in solving real-world problems involving rates of change.

3. Can you provide an example of using limit definition for derivation of f(x)?

Sure, for example, if we have the function f(x) = x^2, we can use the limit definition to find the derivative at a specific point, say x = 2. By taking the limit of the slope of the secant line between (2, f(2)) and (2+h, f(2+h)) as h approaches 0, we can find that the derivative of f(x) at x = 2 is 4.

4. What are some common mistakes when using limit definition for derivation of f(x)?

Some common mistakes when using limit definition for derivation of f(x) include not properly understanding the concept, making algebraic errors, and not simplifying the expression before taking the limit. It is important to carefully follow the steps and pay attention to detail when using this definition.

5. How can I help my daughter understand limit definition for derivation of f(x)?

You can start by explaining the concept in simple terms and providing real-world examples. It is also helpful to encourage her to practice solving problems using the limit definition and provide guidance when needed. Additionally, there are many online resources and tutoring services available that can provide further assistance.

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