Is the derivative of 2x^2 = 4x or 8x?

  • Thread starter 5P@N
  • Start date
  • Tags
    Derivative
In summary, the conversation discusses the power rule of integration and the confusion surrounding the derivative of 2x^2. While one person correctly states that the derivative is 4x, another person claims it is 8x, possibly due to a misunderstanding or mistake. The conversation also touches on the difference between differentiation and integration.
  • #1
5P@N
58
3
Call me crazy, but I do recall the power rule of integration viz: f(x) = x^n, f(x)' = n*x^n-1. Therefore, it seems as though 2x^2 would have a derivative of 4x. Fine. So why have I encountered someone else claiming that it's 8x? WHAT?! Who's right?
 
Physics news on Phys.org
  • #2
5P@N said:
Call me crazy, but I do recall the power rule of integration viz: f(x) = x^n, f(x)' = n*x^n-1.
Do you really mean ##n * x^n - 1##? That's what you wrote. As inline text, use parentheses -- n*x^(n - 1)

5P@N said:
Therefore, it seems as though 2x^2 would have a derivative of 4x.
Yes. ##d/dx(2x^2) = 4x##.
5P@N said:
Fine. So why have I encountered someone else claiming that it's 8x? WHAT?! Who's right?
Maybe they're working a different problem.
 
  • #3
5P@N said:
So why have I encountered someone else claiming that it's 8x?
I can think of many reasons, but none of them involve mathematics.
 
  • Like
Likes wvasiladiotis
  • #4
I haven't yet applied Latex (I'm going to read the article after I finish reading this other long article on u-substitution - I'm really trying here), but what I mean is the super basic power rule of derivatives: f(x) = xn, f(x)' = nxn-1
 
  • #5
You are right, the other person must have a brain worm. Also, I would write ##f'(x)## instead of ##f(x)'##.

EDIT: Could you prove that the other has a brain worm?
 
Last edited:
  • #6
And just for the record: I meant DERIVATION, not integration.o0)
 
  • #7
5P@N said:
And just for the record: I meant DERIVATION, not integration.o0)
Contrary to much popular opinion, the opposite of integration is differentiation, not derivation. You can derive the quadratic formula using the completion of squares technique, but you differentiate ##2x^2## to get the derivative, 4x. Yes, English is weird...
 
  • #8
Mark44 said:
Contrary to much popular opinion, the opposite of integration is differentiation, not derivation. You can derive the quadratic formula using the completion of squares technique, but you differentiate ##2x^2## to get the derivative, 4x. Yes, English is weird...
Thanks for clarifying. I sometimes get confused because the result of differentiation is a derivative (obeying the product rule) and the result of integration is an anti-derivative. Is that correct or am I still confusing terms?
 
  • #9
fresh_42 said:
Thanks for clarifying. I sometimes get confused because the result of differentiation is a derivative (obeying the product rule) and the result of integration is an anti-derivative. Is that correct or am I still confusing terms?
No, you have it right.
 
  • #10
Perhaps "someone else" meant (2x)2, which has the derivative 8x.
 
  • Like
Likes TjerkR, HallsofIvy, jtbell and 1 other person

1. What is a derivative?

A derivative is a mathematical concept that represents the instantaneous rate of change of a function at a specific point. It measures how much a function changes with respect to its input variable.

2. How do you find the derivative of a function?

To find the derivative of a function, you can use the rules of differentiation, such as the power rule, product rule, and chain rule. Alternatively, you can also use the definition of a derivative, which involves taking the limit of the difference quotient as the change in the input variable approaches zero.

3. Is the derivative of a function always unique?

Yes, the derivative of a function is always unique. This means that no matter which method you use to find the derivative, you will always get the same result.

4. What is the derivative of 2x^2?

The derivative of 2x^2 is 4x. This can be found using the power rule, which states that the derivative of x^n is nx^(n-1). In this case, n=2, so the derivative is 2*2x^(2-1) = 4x.

5. Why is there confusion about the derivative of 2x^2?

There is confusion about the derivative of 2x^2 because it can also be written as 2x*x, which can be interpreted as either 2*(x*x) or (2x)*x. In the first case, the derivative is 2x, while in the second case, the derivative is 4x. This is due to the ambiguity of the multiplication symbol, which is why it is important to use proper parentheses when writing mathematical expressions.

Similar threads

  • Calculus and Beyond Homework Help
Replies
10
Views
444
Replies
5
Views
1K
  • Calculus
Replies
2
Views
1K
Replies
4
Views
2K
Replies
1
Views
935
Replies
11
Views
2K
  • Calculus and Beyond Homework Help
Replies
2
Views
511
Replies
3
Views
1K
Replies
16
Views
2K
Back
Top