# Derivatives in Halliday's physics book?

1. Nov 25, 2015

### kent davidge

(sorry my bad english). I was reading a Halliday's book of phyisics awhat I found is below.

d(72t²)/dt = 144t

why did the result was 144? It has anything to do with the deltas in the equation (d and dt)?

and second I dont realize why the result of this another equation is this

4t²+2t+3 = 8t+2

Last edited: Nov 25, 2015
2. Nov 25, 2015

### BvU

These are very simple differentiations. What do you know of differentiating a function ? E.g. the definition of derivative?
The derivative of f(x) = x2 ?

3. Nov 25, 2015

### kent davidge

well, I know a little bit how to solve an integral by summing all the terms but when I solve it for f(x) = x² I found 72t² and the result is 144t as you can see in the image above.

4. Nov 25, 2015

### BvU

But this is not integration, it is differentiation !

5. Nov 25, 2015

Staff Emeritus
This physics text is calculus based. You will need to learn calculus before attacking that text, I'm afraid.

6. Nov 25, 2015

### Orodruin

Staff Emeritus
I cannot do anything but agree with previous posters. These results are very basic derivatives and you will need to learn calculus properly before you can hope to understand what is going on.

Also, please note that the thread levels are intended for you to mark what level of answer you are comfortable with. The "A" you marked this thread with means that you expect an answer on graduate student level. This is clearly not the case and I have changed the level accordingly.

7. Nov 25, 2015

### Staff: Mentor

What did you think it should have been, and how did you arrive at that result?