# Calculus problem, I don't understand what it means?

1. Aug 17, 2008

### dominus96

1. The problem statement, all variables and given/known data

Dx(7x+2-3x5)

2. Relevant equations

CNXN-1?

3. The attempt at a solution

Basically, I am in Physics C and this is our first homework assignment dealing with calculus/derivatives. I was able to do some of them, but I have no idea how to do this one, mainly because I don't know what to do with the Dx.

To make sure I am on the right track, please tell me if this is the correct answer for another problem:

Problem: f(x) = -5x2+2x-1, find df/dx

And my answer is -10x + 2, using the power rule. Is that right?

2. Aug 17, 2008

### tiny-tim

… power rules ok!

Hi dominus96!
Completely!
Dx is just another way of writing d/dx.

Just use the power rule again … which, as you say, is:

3. Aug 17, 2008

### dominus96

Thank you very much tiny-tim. If you don't mind, I have one more similar problem that is also written in a way I don't understand. Here it is:

Find f' for f(x) = 11x - 2.

Is f' (f prime) basically the first derivative again, or different?

4. Aug 17, 2008

### tiny-tim

Yup … same thing!

(the advantage of the ' notation is that it's much easier to type f'' and f''' and so on! )

5. Aug 17, 2008

### HallsofIvy

Staff Emeritus
You should also remember that the derivative of a function, whether it is called "Dx f" or "df/dx" or "f' " is a generalization of the slope of a line- and since f(x)= 11x- 2 has a straight line as its graph, the derivative is ...

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